Chrome plating. Nickel plating, chrome plating, bluing, etc.

Nickel-plated coatings have a number of valuable properties: they polish well, acquiring a beautiful long-lasting mirror shine, are durable and protect metal well from corrosion.

The color of nickel coatings is silvery-white with a yellowish tint; they are easy to polish, but tarnish over time. The coatings are characterized by a fine-crystalline structure, good adhesion to steel and copper substrates, and the ability to passivate in air.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises.

For coating steel products, nickel plating is often performed over an intermediate copper sublayer. Sometimes a three-layer nickel-copper-nickel coating is used. In some cases, the nickel layer is applied thin layer chromium, which forms a nickel-chromium coating. Nickel is applied to parts made of copper and copper-based alloys without an intermediate sublayer. The total thickness of two and three-layer coatings is regulated by the norms of mechanical engineering, usually it is 25-30 microns.

On parts intended for operation in humid tropical climates, the coating thickness must be at least 45 microns. In this case, the regulated thickness of the nickel layer is not less than 12–25 microns.

Nickel-plated parts are polished to obtain shiny coatings. V recent times Brilliant nickel plating is widely used, which eliminates the laborious operation of mechanical polishing. Brilliant nickel plating is achieved by introducing brighteners into the electrolyte. However, the decorative qualities of mechanically polished surfaces are higher than those obtained by shiny nickel plating.

The deposition of nickel occurs at significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

Electrolytes for nickel plating are relatively simple in composition. Currently, sulfate, hydrofluoride and sulfamite electrolytes are used. In lighting factories, exclusively sulfate electrolytes are used, which allow working with high current densities and obtaining coatings at the same time. High Quality... These electrolytes contain nickel-containing salts, buffers, stabilizers, and salts that help dissolve the anodes.

Sulfate electrolytes have high electrical conductivity and good dissipation ability.

The electrolyte of the following composition, g / l, is widely used:

NiSO4 7H2O
240–250

* Or NiCl2 6H2O - 45 g / l.

Nickel plating is carried out at a temperature of 60 ° C, pH = 5.6 ÷ 6.2 and a cathode current density of 3-4 A / dm2.

Depending on the composition of the bath and the mode of its operation, coatings can be obtained with varying degrees of gloss. For these purposes, several electrolytes have been developed, the compositions of which are given below, g / l:

for matte finish:

NiSO4 7H2O
180–200

Na2SO4 10H2O
80–100

H3BO3
30–35

Nickel plated at a temperature of 25–30 ° C, at a cathode current density of 0.5–1.0 A / dm2 and pH = 5.0–5.5;

for a semi-gloss coating:

Nickel sulfate NiSO4 · 7H2O 200-300

Boric acid H3BO3 30

2.6-2.7-Disulfonaphthalic acid 5

Sodium fluoride NaF 5

Sodium chloride NaCl 7-10

Nickel plating is carried out at a temperature of 20–35 ° C, a cathode current density of 1–2 A / dm2 and pH = 5.5–5.8;

for a shiny finish:

Nickel sulfate (hydrate) 260-300

Nickel chloride (hydrate) 40-60

Boric acid 30–35

Saccharin 0.8-1.5

1,4-butyndiol (in terms of 100%) 0.12-0.15

Phthalimide
0,08–0,1

The operating temperature of nickel plating is 50–60 ° C, the pH of the electrolyte is 3.5–5, the density of the cathodic current with vigorous stirring and continuous filtration is 2–12 A / dm2, and the density of the anode current is 1–2 A / dm2.

A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature.

To maintain the composition of the electrolyte within the required limits, buffer compounds are introduced into it, which are most often used as boric acid or a mixture of boric acid with sodium fluoride. In some electrolytes, citric, tartaric, acetic acid or their alkaline salts are used as buffers.

A feature of nickel coatings is their porosity. In some cases, dotted spots may appear on the surface, the so-called "pitting".

To prevent pitting, intensive air mixing of the baths and shaking of the suspensions with the details attached to them are used. A decrease in pitting is facilitated by the introduction of surface tension reducers or wetting agents into the electrolyte, such as sodium lauryl sulfate, sodium alkyl sulfate, and other sulfates.

The domestic industry produces a good anti-pitting detergent"Progress", which is added to the bath in the amount of 0.5 mg / l.

Nickel plating is very sensitive to foreign impurities that enter the solution from the surface of parts or due to anodic dissolution. When nickel plated steel de-

hoists, the solution is clogged with iron impurities, and when coating alloys based on copper - with its impurities. Removal of impurities is carried out by alkalizing the solution with carbonate or nickel hydroxide.

Pitting organic contaminants are removed by boiling the solution. Sometimes tinting of nickel-plated parts is used. This produces colored surfaces with a metallic sheen.

Toning is carried out by chemical or electrochemical methods. Its essence lies in the formation of a thin film on the surface of the nickel coating, in which light interference occurs. Such films are obtained by depositing organic coatings with a thickness of several micrometers on nickel-plated surfaces, for which the parts are processed in special solutions.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes, in which zinc sulfates are added in addition to nickel sulfates.

The composition of the electrolyte for black nickel plating is as follows, g / l:

Nickel sulfate 40-50

Zinc sulfate 20-30

Rhodanide potassium 25–32

Ammonium sulfate 12-15

Nickel plating is carried out at a temperature of 18–35 ° C, a cathode current density of 0.1 A / dm2 and pH = 5.0–5.5.

2. CHROMIATION

Chrome coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, firmly adhere to the base metal, and are chemically and heat resistant.

In the manufacture of lamps, chrome plating is used to obtain protective and decorative coatings, as well as reflective coatings in the manufacture of mirror reflectors.

Chromium plating is carried out over a previously deposited copper-nickel or nickel-copper-nickel sublayer. The thickness of the chromium layer with such a coating usually does not exceed 1 micron. In the manufacture of reflectors, chrome plating is currently being replaced by other coating methods, but in some factories it is still used for the manufacture of reflectors for mirror lamps.

Chromium has good adhesion to nickel, copper, brass and other materials to be deposited, however, when other metals are deposited onto a chromium plating, poor adhesion is always observed.

A positive property of chromium coatings is that the parts are shiny directly in electroplating baths, for this they do not need to be mechanically polished. Along with this, chromium plating differs from other galvanic processes in more stringent requirements for the operating mode of the baths. Minor deviations from the required current density, electrolyte temperature and other parameters inevitably lead to deterioration of coatings and mass rejects.

The scattering power of chromium electrolytes is low, which leads to poor coverage of internal surfaces and recesses of parts. To increase the uniformity of the coatings, special pendants and additional screens are used.

For chromium plating, solutions of chromic anhydride with the addition of sulfuric acid are used.

Three types of electrolytes have found industrial application: diluted, universal, and concentrated (Table 1). To obtain decorative coatings and to obtain reflectors, a concentrated electrolyte is used. For chromium plating, insoluble lead anodes are used.

Table 1 - Compositions of electrolytes for chromium plating

During operation, the concentration of chromic anhydride in the baths decreases, therefore, to restore the baths, daily adjustments are made by adding fresh chromic anhydride to them.

Several formulations of self-regulating electrolytes have been developed, in which the concentration ratio is automatically maintained.

The composition of this electrolyte is as follows, g / l:

Chromium plating is performed at a cathodic current density of 50–80 A / dm2 and a temperature of 60–70 ° C.

Depending on the relationship between temperature and current density, you can get different kinds chrome plating: dairy shiny and matte.

The milk coating is obtained at a temperature of 65-80 ° C and

low current density. A glossy finish is obtained at 45–60 ° C and medium amperage. The matte finish is obtained at a temperature of 25-45 ° C and high density current. In the production of luminaires, a shiny chrome finish is most often used.

To obtain mirror reflectors, chromium plating is carried out at a temperature of 50–55 ° C and a current density of 60 A / dm2. in the manufacture of mirror reflectors, preliminary deposition of copper and nickel is performed. The reflective surface is polished after each layer is applied. The technological process includes following operations:

grinding and polishing the surface;

copper plating;

nickel plating;

polishing, degreasing, pickling;

chrome plating;

clean polishing.

Products made of copper and copper alloys are chrome plated without an intermediate layer. The parts are immersed in the electrolyte after the voltage is applied to the bath. When applying multilayer coatings to steel products, the layer thickness is regulated by GOST 3002-70. Thickness values are given in table 2.

Table 2 - Minimum thickness multilayer electroplated coatings

Chromium plating baths are equipped with a powerful exhaust ventilation to remove vapors of toxic chromic acid.

When chrome plating, some of the hexavalent chromium Cr6 + gets into wastewater, therefore, to prevent Cr6 + emissions into open water bodies, protective measures- install neutralizers and treatment facilities.

1. Afanasyeva E.I., Skobelev V.M. "Sources of light and control gear: Textbook for technical schools", 2nd ed., Revised., M: Energoatomizdat, 1986, 270s.

2. Bolenok V.E. "Production of electric lighting devices: Textbook for technical schools", M: Energoizdat, 1981, 303s.

3. Denisov V.P. "Production of electrical light sources", M: Energy, 1975, 488s.

4. Denisov V.P., Melnikov Yu.F. "Technology and equipment for the production of electrical light sources: Textbook for technical schools", M: Energy, 1983, 384p.

5. Plyaskin P.V. and others "Fundamentals of designing electrical light sources", M: Energoatomizdat, 1983, 360p.

6. Churkina N.I., Lityushkin V.V., Sivko A.P. "Fundamentals of technology of electrical light sources" / under the general. ed. Prytkova A.A., Saransk: Mordovskoe book publishing house, 2003, 344s.

1. NICKEL PLATING

2. CHROMIATION

LIST OF USED SOURCES

1. NICKEL PLATING

Nickel-plated coatings have a number of valuable properties: they polish well, acquire a beautiful long-lasting mirror shine, are durable and well protect the metal from corrosion.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises.

For coating steel products, nickel plating is often performed over an intermediate copper sublayer. Sometimes a three-layer nickel-copper-nickel coating is used. In some cases, a thin layer of chromium is applied to the nickel layer, thereby forming a nickel-chromium coating. Nickel is applied to parts made of copper and copper-based alloys without an intermediate sublayer. The total thickness of two and three-layer coatings is regulated by the norms of mechanical engineering, usually it is 25-30 microns.

Nickel-plated parts are polished to obtain shiny coatings. Recently, brilliant nickel plating has been widely used, which eliminates the laborious operation of mechanical polishing. Brilliant nickel plating is achieved by introducing brighteners into the electrolyte. However, the decorative qualities of mechanically polished surfaces are higher than those obtained by shiny nickel plating.

The deposition of nickel occurs at significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

Electrolytes for nickel plating are relatively simple in composition. Currently, sulfate, hydrofluoride and sulfamite electrolytes are used. In lighting factories, only sulfate electrolytes are used, which allow them to work with high current densities and at the same time obtain high quality coatings. These electrolytes contain nickel-containing salts, buffers, stabilizers, and salts that help dissolve the anodes.

Sulfate electrolytes have high electrical conductivity and good dissipation ability.

The electrolyte of the following composition, g / l, is widely used:

NiSO4 · 7H2O 240–250

* Or NiCl2 6H2O - 45 g / l.

Nickel plating is carried out at a temperature of 60 ° C, pH = 5.6 h6.2 and a cathode current density of 3-4 A / dm2.

for matte finish:

NiSO4 · 7H2O 180-200

Na2SO4 · 10H2O 80–100

Nickel plated at a temperature of 25–30 ° C, at a cathode current density of 0.5–1.0 A / dm2 and pH = 5.0–5.5;

for a semi-gloss coating:

Nickel sulfate NiSO4 · 7H2O 200-300

Boric acid H3BO3 30

2.6-2.7-Disulfonaphthalic acid 5

Sodium fluoride NaF 5

Sodium chloride NaCl 7-10

Nickel plating is carried out at a temperature of 20–35 ° C, a cathode current density of 1–2 A / dm2 and pH = 5.5 h5.8;

for a shiny finish:

Nickel sulfate (hydrate) 260-300

Nickel chloride (hydrate) 40-60

Boric acid 30–35

Saccharin 0.8-1.5

1,4-butyndiol (in terms of 100%) 0.12-0.15

Phthalimide 0.08-0.1

A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature.

A feature of nickel coatings is their porosity. In some cases, dotted spots may appear on the surface, the so-called "pitting".

The domestic industry produces a good anti-pitting detergent "Progress", which is added to the bath in an amount of 0.5 mg / l.

Nickel plating is very sensitive to foreign impurities that enter the solution from the surface of parts or due to anodic dissolution. When nickel plated steel de-

Pitting organic contaminants are removed by boiling the solution. Sometimes tinting of nickel-plated parts is used. This produces colored surfaces with a metallic sheen.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes, in which zinc sulfates are added in addition to nickel sulfates.

The composition of the electrolyte for black nickel plating is as follows, g / l:

Nickel sulfate 40-50

Zinc sulfate 20-30

Rhodanide potassium 25–32

Ammonium sulfate 12-15

Nickel plating is carried out at a temperature of 18–35 ° C, a cathode current density of 0.1 A / dm2 and pH = 5.0 h5.5.

2. CHROMIATION

Chrome coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, firmly adhere to the base metal, and are chemically and heat resistant.

In the manufacture of lamps, chrome plating is used to obtain protective and decorative coatings, as well as reflective coatings in the manufacture of mirror reflectors.

Chromium has good adhesion to nickel, copper, brass and other materials to be deposited, however, when other metals are deposited onto a chromium plating, poor adhesion is always observed.

For chromium plating, solutions of chromic anhydride with the addition of sulfuric acid are used.

Table 1 - Compositions of electrolytes for chromium plating

During operation, the concentration of chromic anhydride in the baths decreases, therefore, to restore the baths, daily adjustments are made by adding fresh chromic anhydride to them.

Several formulations of self-regulating electrolytes have been developed, in which the concentration ratio is automatically maintained.

The composition of this electrolyte is as follows, g / l:

Chromium plating is performed at a cathodic current density of 50–80 A / dm2 and a temperature of 60–70 ° C.

Depending on the relationship between temperature and current density, different types of chrome coatings can be obtained: glossy milky and matte.

The milk coating is obtained at a temperature of 65-80 ° C and

low current density. A glossy finish is obtained at 45–60 ° C and medium amperage. A matt finish is obtained at a temperature of 25–45 ° C and a high current density. In the production of luminaires, a shiny chrome finish is most often used.

grinding and polishing the surface;

copper plating;

nickel plating;

polishing, degreasing, pickling;

chrome plating;

clean polishing.

Table 2 - Minimum thickness of multilayer electroplated coatings

Chromium plating baths are equipped with powerful exhaust ventilation to remove toxic chromic acid vapors.

When chromium plating, part of the hexavalent chromium Cr6 + enters the wastewater, therefore, to prevent Cr6 + emissions into open water bodies, protective measures are used - neutralizers and treatment facilities are installed.

LIST OF USED SOURCES

Afanasyeva E.I., Skobelev V.M. "Sources of light and control gear: Textbook for technical schools", 2nd ed., Revised., M: Energoatomizdat, 1986, 270s.

Bolenok V.E. "Production of electric lighting devices: Textbook for technical schools", M: Energoizdat, 1981, 303s.

Denisov V.P. "Production of electrical light sources", M: Energy, 1975, 488s.

Characterization of solid waste from the chromium plating process. Titration with ferrous sulfate and permanganate. Theory of the determination of chromium experimentally. Qualitative analysis of the solid waste components of the chromium plating process. Colorimetric methods for the determination of chromium.

Surrounding us metal objects rarely consist of pure metals. Only aluminum pans or copper wire are around 99.9% pure. In most other cases, people are dealing with alloys. So, various types of iron and steel, along with metal additives, contain insignificant ...

Ministry of Education Russian Federation State educational institution higher and vocational education IRKUTSK STATE UNIVERSITY

Physicochemical and thermodynamic properties of concentrated aqueous solutions containing electrolyte components for the deposition of an iron-nickel alloy. Kinetic regularities of anodic dissolution of an iron-nickel alloy under nonstationary conditions.

Nickel-plated coatings have a number of valuable properties: they polish well, acquire a beautiful long-lasting mirror shine, are durable and well protect the metal from corrosion.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises.

For coating steel products, nickel plating is often performed over an intermediate copper sublayer. Sometimes a three-layer nickel-copper-nickel coating is used. In some cases, a thin layer of chromium is applied to the nickel layer, thereby forming a nickel-chromium coating. Nickel is applied to parts made of copper and copper-based alloys without an intermediate sublayer. The total thickness of two and three-layer coatings is regulated by the norms of mechanical engineering, usually it is 25-30 microns.

The deposition of nickel occurs at significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

Sulfate electrolytes have high electrical conductivity and good dissipation ability.

The electrolyte of the following composition, g / l, is widely used:

NiSO4 · 7H2O240–250

* Or NiCl2 6H2O - 45 g / l.

Nickel plating is carried out at a temperature of 60 ° C, pH = 5.6 ÷ 6.2 and a cathode current density of 3-4 A / dm2.

for matte finish:

NiSO4 · 7H2O180-200

Na2SO4 · 10H2O80–100

Nickel plated at a temperature of 25–30 ° C, at a cathode current density of 0.5–1.0 A / dm2 and pH = 5.0–5.5;

for a semi-gloss coating:

Nickel sulfate NiSO4 · 7H2O200-300

Boric acid H3BO330

2.6-2.7-Disulfonaphthalic acid5

Sodium fluoride NaF5

Sodium chloride NaCl7-10

Nickel plating is carried out at a temperature of 20–35 ° C, a cathode current density of 1–2 A / dm2 and pH = 5.5–5.8;

for a shiny finish:

Nickel sulfate (hydrate) 260-300

Nickel chloride (hydrate) 40-60

Boric acid 30–35

Saccharin 0.8-1.5

1,4-butyndiol (in terms of 100%) 0.12-0.15

Phthalimide 0.08-0.1

Working temperature nickel plating 50–60 ° C, electrolyte pH 3.5–5, cathodic current density with vigorous stirring and continuous filtration 2–12 A / dm2, anodic current density 1–2 A / dm2.

A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature.

A feature of nickel coatings is their porosity. In some cases, dotted spots may appear on the surface, the so-called "pitting".

The domestic industry produces a good anti-pitting detergent "Progress", which is added to the bath in an amount of 0.5 mg / l.

Nickel plating is very sensitive to foreign impurities that enter the solution from the surface of parts or due to anodic dissolution. When nickel plated steel de-

Pitting organic contaminants are removed by boiling the solution. Sometimes tinting of nickel-plated parts is used. This produces colored surfaces with a metallic sheen.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes, in which zinc sulfates are added in addition to nickel sulfates.

The composition of the electrolyte for black nickel plating is as follows, g / l:

Nickel sulfate 40-50

Zinc sulfate 20-30

Rhodanide potassium 25–32

Ammonium sulfate 12-15

Nickel plating is carried out at a temperature of 18–35 ° C, a cathode current density of 0.1 A / dm2 and pH = 5.0–5.5.

2. CHROMIATION

Chrome coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, firmly adhere to the base metal, and are chemically and heat resistant.

In the manufacture of lamps, chrome plating is used to obtain protective and decorative coatings, as well as reflective coatings in the manufacture of mirror reflectors.

Chromium has good adhesion to nickel, copper, brass and other materials to be deposited, however, when other metals are deposited onto a chromium plating, poor adhesion is always observed.

For chromium plating, solutions of chromic anhydride with the addition of sulfuric acid are used.

Table 1 - Compositions of electrolytes for chromium plating

During operation, the concentration of chromic anhydride in the baths decreases, therefore, to restore the baths, daily adjustments are made by adding fresh chromic anhydride to them.

Several formulations of self-regulating electrolytes have been developed, in which the concentration ratio is automatically maintained

The composition of this electrolyte is as follows, g / l:

Chromium plating is performed at a cathodic current density of 50–80 A / dm2 and a temperature of 60–70 ° C.

Depending on the relationship between temperature and current density, different types of chrome coatings can be obtained: glossy milky and matte.

PLAN 1. NICKEL PLATING 2. CHROME PLATING 6 LIST OF USED SOURCES 1. NICKEL PLATING Nickel plated coatings have a number of valuable properties: they are well polished, acquiring a beautiful long-lasting mirror shine, are durable and well protect the metal from corrosion. The color of nickel coatings is silvery-white with a yellowish tint; they are easy to polish, but tarnish over time. The coatings are characterized by a fine-crystalline structure, good adhesion to steel and copper base and the ability to passivate in air.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises. For coating steel products, nickel plating is often performed over an intermediate copper sublayer. Sometimes a three-layer nickel-copper-nickel coating is used. In some cases, a thin layer of chromium is applied to the nickel layer, thereby forming a nickel-chromium coating. Nickel is applied to parts made of copper and copper-based alloys without an intermediate sublayer.

The total thickness of two and three-layer coatings is regulated by the norms of mechanical engineering, usually it is 25-30 microns. On parts intended for operation in humid tropical climates, the coating thickness must be at least 45 microns. In this case, the regulated thickness of the nickel layer is not less than 12–25 microns. Nickel-plated parts are polished to obtain shiny coatings.

Recently, brilliant nickel plating has been widely used, which eliminates the laborious operation of mechanical polishing. Brilliant nickel plating is achieved by introducing brighteners into the electrolyte. However, the decorative qualities of mechanically polished surfaces are higher than those obtained by shiny nickel plating. The deposition of nickel occurs at significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

The advantages of these electrolytes are the lack of components, high stability and low aggressiveness. Electrolytes allow a high concentration of nickel salt in their composition, which makes it possible to increase the cathode current density and, consequently, to increase the productivity of the process. Sulfate electrolytes have high electrical conductivity and good dissipation ability. The electrolyte of the following composition, g / l, is widely used: NiSO4 7H2O 240–250 NaCl * 22.5 H3BO3 30 * Or NiCl2 6H2O - 45 g / l. Nickel plating is carried out at a temperature of 60 ° C, pH = 5.6 ÷ 6.2 and a cathode current density of 3-4 A / dm2. Depending on the composition of the bath and the mode of its operation, coatings can be obtained with varying degrees of gloss.

For these purposes, several electrolytes have been developed, the compositions of which are given below, g / l: for a matte coating: NiSO4 7H2O 180–200 Na2SO4 10H2O 80–100 H3BO3 30–35 NaCl 5–7 Nickel at a temperature of 25–30 ° C, at a cathode density current 0.5–1.0 A / dm2 and pH = 5.0–5.5; for a semi-gloss coating: Nickel sulfate NiSO4 7H2O 200-300 Boric acid H3BO3 30 2.6-2.7-Disulfonaphthalic acid 5 Sodium fluoride NaF 5 Sodium chloride NaCl 7-10 Nickel plating is carried out at a temperature of 20-35 ° C, cathode current density 1 –2 A / dm2 and pH = 5.5 ÷ 5.8; for a shiny coating: Nickel sulfate (hydrate) 260-300 Nickel chloride (hydrate) 40-60 Boric acid 30-35 Saccharin 0.8-1.5 1.4-butynediol (in terms of 100%) 0.12-0 , 15 Phthalimide 0.08–0.1 Operating temperature of nickel plating 50–60 ° C, electrolyte pH 3.5–5, cathodic current density with vigorous stirring and continuous filtration 2–12 A / dm2, anode current density 1–2 A / dm2. A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature. To maintain the composition of the electrolyte within the required limits, buffer compounds are introduced into it, which are most often used as boric acid or a mixture of boric acid with sodium fluoride.

In some electrolytes, citric, tartaric, acetic acid or their alkaline salts are used as buffers. A feature of nickel coatings is their porosity.

In some cases, dotted spots may appear on the surface, the so-called "pitting". To prevent pitting, intensive air mixing of the baths and shaking of the suspensions with the details attached to them are used.

A decrease in pitting is facilitated by the introduction of surface tension reducers or wetting agents into the electrolyte, such as sodium lauryl sulfate, sodium alkyl sulfate, and other sulfates.

The domestic industry produces a good anti-pitting detergent "Progress", which is added to the bath in an amount of 0.5 mg / l. Nickel plating is very sensitive to foreign impurities that enter the solution from the surface of parts or due to anodic dissolution.

When steel parts are nickel-plated, the solution is clogged with iron impurities, and when copper-based alloys are coated, with iron impurities. Removal of impurities is carried out by alkalizing the solution with carbonate or nickel hydroxide. Pitting organic contaminants are removed by boiling the solution.

Sometimes tinting of nickel-plated parts is used. This produces colored surfaces with a metallic sheen. Toning is carried out by chemical or electrochemical methods. Its essence lies in the formation of a thin film on the surface of the nickel coating, in which light interference occurs. Such films are obtained by depositing organic coatings with a thickness of several micrometers on nickel-plated surfaces, for which the parts are processed in special solutions.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes, in which zinc sulfates are added in addition to nickel sulfates. The composition of the electrolyte for black nickel plating is as follows, g / l: Nickel sulfate 40-50 Zinc sulfate 20-30 Potassium rhodanide 25-32 Ammonium sulfate 12-15 Nickel plating is carried out at a temperature of 18-35 ° C, cathode current density 0.1 A / dm2 and pH = 5.0 ÷ 5.5. 2. CHROMIATION Chromium coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, firmly adhere to the base metal, and are chemically and heat resistant.

In the manufacture of lamps, chrome plating is used to obtain protective and decorative coatings, as well as reflective coatings in the manufacture of mirror reflectors. Chromium plating is carried out over a previously deposited copper-nickel or nickel-copper-nickel sublayer. The thickness of the chromium layer with such a coating usually does not exceed 1 micron. In the manufacture of reflectors, chrome plating is currently being replaced by other coating methods, but in some factories it is still used for the manufacture of reflectors for mirror lamps.

Chromium has good adhesion to nickel, copper, brass and other materials to be deposited, however, when other metals are deposited onto a chromium plating, poor adhesion is always observed. A positive property of chromium coatings is that the parts are shiny directly in electroplating baths, for this they do not need to be mechanically polished.

Along with this, chromium plating differs from other galvanic processes in more stringent requirements for the operating mode of the baths. Minor deviations from the required current density, electrolyte temperature and other parameters inevitably lead to deterioration of coatings and mass rejects. The scattering power of chromium electrolytes is low, which leads to poor coverage of internal surfaces and recesses of parts.

To increase the uniformity of the coatings, special pendants and additional screens are used. For chromium plating, solutions of chromic anhydride with the addition of sulfuric acid are used. Three types of electrolytes have found industrial application: diluted, universal, and concentrated (Table 1). To obtain decorative coatings and to obtain reflectors, a concentrated electrolyte is used. For chromium plating, insoluble lead anodes are used. Table 1 - Compositions of electrolytes for chromium plating components Electrolyte compositions, g / l diluted universal concentrated chromic anhydride sulfuric acid cathodic current density, A / dm2 solution temperature, ° С 150 1.5 45–100 55–60 250 2.5 15–60 45–55 350 3.5 10–30 35–45 During operation, the concentration of chromic anhydride in the baths decreases, therefore, to restore the baths, daily adjustments are made by adding fresh chromic anhydride to them. Several formulations of self-regulating electrolytes have been developed, in which the concentration ratio is automatically maintained. The composition of such an electrolyte is as follows, g / l: Cr2O3 250 SrSO4 5-6 K2SiF6 20 Chromium plating is performed at a cathode current density of 50–80 A / dm2 and a temperature of 60–70 ° C. Depending on the relationship between temperature and current density, different types of chrome coatings can be obtained: glossy milky and matte. The milk coating is obtained at a temperature of 65–80 ° C and a low current density. A glossy finish is obtained at 45–60 ° C and medium amperage. A matt finish is obtained at a temperature of 25–45 ° C and a high current density. In the production of luminaires, a shiny chrome finish is most often used.

The reflective surface is polished after each layer is applied.

The technological process includes the following operations: grinding and polishing the surface; copper plating; polishing, degreasing, pickling; nickel plating; polishing, degreasing, pickling; chrome plating; clean polishing.

After each technological operation, a 100% quality control of the coating is carried out, since non-observance of the technology requirements leads to peeling of the sublayer together with the chrome coating. Products made of copper and copper alloys are chrome plated without an intermediate layer.

The parts are immersed in the electrolyte after the voltage is applied to the bath. When applying multilayer coatings to steel products, the layer thickness is regulated by GOST 3002-70. Thickness values are given in table 2. Table 2 - Minimum thickness of multi-layer electroplated coatings working conditions symbol groups of coatings coating thickness, microns minimum average calculated nickel without sublayer multilayer copper-nickel or nickel-copper-nickel chrome total top layer of nickel light medium hard L S W 10 30 - 10 30 45 5 10 15 0.5 0.5 0.5 Chromium plating baths are equipped with powerful exhaust ventilation to remove fumes of toxic chromic acid.

2. 3. "Technology and equipment for the production of electric light sources ... and others. 6.

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(technology tips)
Erlykin L.A. "Do it yourself" 3-92

Which of the home craftsmen did not face the need to nickel or chrome this or that part. What do-it-yourselfer didn’t dream of installing a “non-working” bushing with a hard, wear-resistant surface obtained by saturating it with boron in a responsible unit. But how to do at home what, as a rule, is carried out at specialized enterprises by the methods of chemical-thermal and electrochemical processing of metals. You will not build gas and vacuum furnaces at home, build electrolysis baths. But it turns out that it is not necessary to build all this at all. It is enough to have on hand some reagents, an enamel pan and, perhaps, blowtorch, as well as know the recipes for "chemical technology", with the help of which metals can also be copper-plated, cadmium-plated, tinned, oxidized, etc.

So, let's begin to get acquainted with the secrets of chemical technology. Please note that the content of the components in the solutions given, as a rule, is given in g / l. In case other units apply, a special clause follows.

Preparatory operations

Before applying paints, protective and decorative films to metal surfaces, as well as before coating them with other metals, it is necessary to carry out preparatory operations, that is, to remove contaminants of various nature from these surfaces. Please note that the final result of all work largely depends on the quality of the preparatory operations.

Preparatory operations include degreasing, cleaning and pickling.

Degreasing

Surface degreasing process metal parts carried out, as a rule, when these parts have just been processed (sanded or polished) and there is no rust, scale and other foreign products on their surface.

By means of degreasing, oil and grease films are removed from the surface of the parts. For this, aqueous solutions of some chemical reagents are used, although organic solvents can also be used for this. The latter have the advantage that they do not have a subsequent corrosive effect on the surface of the parts, but at the same time they are toxic and flammable.

Aqueous solutions. Degreasing of metal parts in aqueous solutions is carried out in an enamel bowl. Pour in water, dissolve chemical reagents in it and put on a low fire. Upon reaching the right temperature load the parts into the solution. During processing, the solution is stirred. Below are the compositions of degreasing solutions (g / l), as well as the working temperatures of the solutions and the processing time of parts.

Degreasing solutions (g / l)

For ferrous metals (iron and iron alloys)

Liquid glass (clerical silicate glue) - 3 ... 10, caustic soda (potassium) - 20 ... 30, trisodium phosphate - 25 ... 30. Solution temperature - 70 ... 90 ° С, processing time - 10 ... 30 minutes.

Liquid glass - 5 ... 10, caustic soda - 100 ... 150, soda ash- 30 ... 60. Solution temperature - 70 ... 80 ° С, processing time - 5 ... 10 minutes.

Liquid glass - 35, trisodium phosphate - 3 ... 10. Solution temperature - 70 ... 90 ° С, processing time - 10 ... 20 minutes.

Liquid glass - 35, trisodium phosphate - 15, preparation - emulsifier OP-7 (or OP-10) -2. Solution temperature - 60-70 ° С, processing time - 5 ... 10 minutes.

Liquid glass - 15, preparation OP-7 (or OP-10) -1. Solution temperature - 70 ... 80 ° С, processing time - 10 ... 15 minutes.

Soda ash - 20, potassium chromium peak - 1. Solution temperature - 80 ... 90 ° С, processing time - 10 ... 20 minutes.

Soda ash - 5 ... 10, trisodium phosphate - 5 ... 10, preparation OP-7 (or OP-10) - 3. Solution temperature - 60 ... 80 ° С, processing time - 5 ... 10 minutes ...

For copper and copper alloys

Caustic soda - 35, soda ash - 60, trisodium phosphate - 15, preparation OP-7 (or OP-10) - 5. Solution temperature - 60 ... 70, processing time - 10 ... 20 minutes.

Caustic soda (potassium) - 75, liquid glass- 20 Solution temperature - 80 ... 90 ° С, processing time - 40 ... 60 minutes.

Liquid glass - 10 ... 20, trisodium phosphate - 100. Solution temperature - 65 ... 80 С, processing time - 10 ... 60 minutes.

Liquid glass - 5 ... 10, soda ash - 20 ... 25, preparation OP-7 (or OP-10) -5 ... 10. Solution temperature - 60 ... 70 ° С, processing time - 5 ... 10 minutes.

Trisodium phosphate - 80 ... 100. Solution temperature - 80 ... 90 ° С, processing time - 30 ... 40 minutes.

For aluminum and its alloys

Liquid glass - 25 ... 50, soda ash - 5 ... 10, trisodium phosphate-5 ... 10, preparation OP-7 (or OP-10) - 15 ... 20 min.

Liquid glass - 20 ... 30, soda ash - 50 ... 60, trisodium phosphate - 50 ... 60. Solution temperature - 50 ... 60 ° С, processing time - 3 ... 5 minutes.

Soda ash - 20 ... 25, trisodium phosphate - 20 ... 25, preparation OP-7 (or OP-10) -5 ... 7. Temperature - 70 ... 80 ° С, processing time - 10 ... 20 minutes.

For silver, nickel and their alloys

Liquid glass - 50, soda ash - 20, trisodium phosphate - 20, preparation OP-7 (or OP-10) - 2. Solution temperature - 70 ... 80 ° С, processing time - 5 ... 10 minutes.

Liquid glass - 25, soda ash - 5, trisodium phosphate - 10. Solution temperature - 75 ... 85 ° С, processing time - 15 ... 20 minutes.

For zinc

Liquid glass - 20 ... 25, caustic soda - 20 ... 25, soda ash - 20 ... 25. Solution temperature - 65 ... 75 ° С, processing time - 5 minutes.

Liquid glass - 30 ... 50, soda ash - 30 .., 50, kerosene - 30 ... 50, preparation OP-7 (or OP-10) - 2 ... 3. Solution temperature - 60-70 ° С, processing time - 1 ... 2 minutes.

Organic solvents

The most commonly used organic solvents are B-70 gasoline (or "gasoline for lighters") and acetone. However, they have a significant drawback - they are highly flammable. Therefore, they have recently been replaced by non-flammable solvents such as trichlorethylene and perchlorethylene. Their dissolving power is much higher than that of gasoline and acetone. Moreover, these solvents can be safely heated, which greatly speeds up the degreasing of metal parts.

Degreasing the surface of metal parts using organic solvents is carried out in this sequence. The parts are loaded into a dish with a solvent and kept for 15 ... 20 minutes. Then the surface of the parts is wiped with a brush directly in the solvent. After this treatment, the surface of each part is carefully treated with a swab soaked in 25% ammonia (it is necessary to work with rubber gloves!).

All degreasing work organic solvents carried out in a well-ventilated area.

Cleaning

In this section, as an example, the process of removing carbon deposits from internal combustion engines will be considered. As you know, carbon deposits are asphalt-resinous substances that form hard-to-remove films on the working surfaces of engines. Removing carbon deposits is a rather difficult task, since the carbon film is inert and firmly adhered to the surface of the part.

Cleaning solution compositions (g / l)

For ferrous metals

Liquid glass - 1.5, soda ash - 33, caustic soda - 25, household soap - 8.5. Solution temperature - 80 ... 90 ° С, processing time - Зч.

Caustic soda - 100, potassium dichromate - 5. Solution temperature - 80 ... 95 ° С, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, sodium dichromate - 5, laundry soap- 8, soda ash - 30. Solution temperature - 80 ... 95 ° С, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, laundry soap - 10, potash - 30. Solution temperature - 100 ° С, processing time - up to 6 hours.

For aluminum (duralumin) alloys

Liquid glass 8.5, laundry soap - 10, soda ash - 18.5. Solution temperature - 85 ... 95 С, processing time - up to 3 hours.

Liquid glass - 8, potassium dichromate - 5, laundry soap - 10, soda ash - 20. Solution temperature - 85 ... 95 ° С, processing time - up to 3 hours.

Soda ash - 10, potassium dichromate - 5, laundry soap - 10. Solution temperature - 80 ... 95 ° С, processing time - up to 3 hours.

Etching

Etching (as a preparatory operation) removes impurities (rust, scale and other corrosion products) that are firmly adhered to their surface from metal parts.

The main purpose of etching is to remove corrosion products; in this case, the base metal should not be etched. To prevent etching of the metal, special additives are introduced into the solutions. Good results are obtained with the use of small amounts of hexamethylenetetramine (urotropine). All solutions for etching ferrous metals add 1 tablet (0.5 g) of urotropin per 1 liter of solution. In the absence of urotropine, it is replaced with the same amount of dry alcohol (sold in sports stores as fuel for tourists).

In view of the fact that inorganic acids are used in recipes for etching, it is necessary to know their initial density (g / cm 3): nitric acid - 1.4, sulfuric acid - 1.84; hydrochloric acid - 1.19; orthophosphoric acid- 1.7; acetic acid - 1.05.

Etching solution compositions

For ferrous metals

Sulfuric acid - 90 ... 130, hydrochloric acid - 80 ... 100. Solution temperature - 30 ... 40 ° С, processing time - 0.5 ... 1.0 h.

Sulfuric acid - 150 ... 200. Solution temperature - 25 ... 60 ° С, processing time - 0.5 ... 1.0 hours.

Hydrochloric acid - 200. Solution temperature - 30 ... 35 ° С, processing time - 15 ... 20 minutes.

Hydrochloric acid - 150 ... 200, formalin - 40 ... 50. Solution temperature 30 ... 50 ° С, processing time 15 ... 25 min.

Nitric acid - 70 ... 80, hydrochloric acid - 500 ... 550. Solution temperature - 50 ° С, processing time - 3 ... 5 minutes.

Nitric acid - 100, sulfuric acid - 50, hydrochloric acid - 150. Solution temperature - 85 ° C, processing time - 3 ... 10 minutes.

Hydrochloric acid - 150, phosphoric acid - 100. Solution temperature - 50 ° С, processing time - 10 ... 20 minutes.

The last solution (when processing steel parts), in addition to cleaning the surface, also phosphates it. And phosphate films on the surface of steel parts allow them to be painted with any paints without a primer, since these films themselves serve as an excellent primer.

Here are some more recipes for etching solutions, the compositions of which this time are given in% (by weight).

Orthophosphoric acid - 10, butyl alcohol - 83, water - 7. Solution temperature - 50 ... 70 ° С, processing time - 20 ... 30 minutes.

Orthophosphoric acid - 35, butyl alcohol - 5, water - 60. Solution temperature - 40 ... 60 ° С, processing time - 30 ... 35 minutes.

After etching ferrous metals, they are washed in a 15% solution of soda ash (or baking soda). Then rinse thoroughly with water.

Note that below, the compositions of solutions are again given in g / L.

For copper and its alloys

Sulfuric acid - 25 ... 40, chromic anhydride - 150 ... 200. Solution temperature - 25 ° С, processing time - 5 ... 10 minutes.

Sulfuric acid - 150, potassium dichromate - 50. Solution temperature - 25, .35 ° С, processing time - 5 ... 15 minutes.

Trilon B-100. Solution temperature - 18 ... 25 ° С, processing time - 5 ... 10 minutes.

Chromic anhydride - 350, sodium chloride - 50. Solution temperature - 18 ... 25 ° С, processing time - 5 ... 15 minutes.

For aluminum and its alloys

Caustic soda -50 ... 100. Solution temperature - 40 ... 60 ° С, processing time - 5 ... 10 s.

Nitric acid - 35 ... 40. Solution temperature - 18 ... 25 ° С, processing time - 3 ... 5 s.

Caustic soda - 25 ... 35, soda ash - 20 ... 30. Solution temperature - 40 ... 60 ° С, processing time - 0.5 ... 2.0 minutes.

Caustic soda - 150, sodium chloride - 30. Solution temperature - 60 ° С, processing time - 15 ... 20 s.

Chemical polishing

Chemical polishing allows you to quickly and efficiently process the surfaces of metal parts. Great advantage This technology lies in the fact that with the help of it (and only it!) it is possible to polish parts with a complex profile at home.

Compositions of solutions for chemical polishing

For carbon steels (the content of the components is indicated in each specific case in certain units (g / l, percent, parts)

Nitric acid - 2 .-. 4, hydrochloric acid 2 ... 5, phosphoric acid - 15 ... 25, the rest is water. Solution temperature - 70 ... 80 ° С, processing time - 1 ... 10 minutes. Content of components - in% (by volume).

Sulfuric acid - 0.1, acetic acid - 25, hydrogen peroxide (30%) - 13. Solution temperature - 18 ... 25 ° С, processing time - 30 ... 60 minutes. The content of the components is in g / l.

Nitric acid - 100 ... 200, sulfuric acid - 200 .., 600, hydrochloric acid - 25, Phosphoric acid - 400. Mixture temperature - 80 ... 120 ° С, processing time - 10 ... 60 s. Content of components in parts (by volume).

For stainless steel

Sulfuric acid - 230, hydrochloric acid - 660, acid orange dye - 25. Solution temperature - 70 ... 75 ° С, processing time - 2 ... 3 minutes. The content of the components is in g / l.

Nitric acid - 4 ... 5, hydrochloric acid - 3 ... 4, phosphoric acid - 20.,. 30, methyl orange - 1, .. 1.5, the rest is water. Solution temperature - 18 ... 25 ° С, processing time - 5..10 minutes. Content of components - in% (by weight).

Nitric acid - 30 ... 90, ferrocyanide potassium (yellow blood salt) - 2 ... 15 g / l, preparation OP-7 - 3 ... 25, hydrochloric acid - 45 ... 110, phosphoric acid - 45. ..280.

Solution temperature - 30 ... 40 ° С, processing time - 15 ... 30 minutes. The content of the components (except for yellow blood salt) - in pl / l.

The latter composition is applicable for polishing cast iron and any steel.

For copper

Nitric acid - 900, sodium chloride - 5, soot - 5. Solution temperature - 18 ... 25 ° С, processing time - 15 ... 20 s. The content of the components is g / l.

Attention! Sodium chloride is added to solutions last, and the solution must be pre-cooled!

Nitric acid - 20, sulfuric acid - 80, hydrochloric acid - 1, chromic anhydride - 50. Solution temperature - 13 ... 18 ° С, processing time - 1 ... 2 minutes. The content of the components is in ml.

Nitric acid 500, sulfuric acid - 250, sodium chloride - 10. Solution temperature - 18 ... 25 ° С, processing time - 10 ... 20 s. The content of the components is in g / l.

For brass

Nitric acid - 20, hydrochloric acid - 0.01, acetic acid - 40, orthophosphoric acid - 40. Mixture temperature - 25 ... 30 ° С, processing time - 20 ... 60 s. The content of the components is in ml.

Copper sulfate ( copper sulfate) - 8, sodium chloride - 16, acetic acid - 3, water - the rest. Solution temperature - 20 ° С, processing time - 20 ... 60 minutes. The content of the components is in% (by weight).

For bronze

Phosphoric acid - 77 ... 79, potassium nitrate - 21 ... 23. The temperature of the mixture is 18 ° C, the processing time is 0.5-3 minutes. The content of the components is in% (by weight).

Nitric acid - 65, sodium chloride - 1 g, acetic acid - 5, phosphoric acid - 30, water - 5. Solution temperature - 18 ... 25 ° С, processing time - 1 ... 5 s. Content of components (except sodium chloride) - in ml.

For nickel and its alloys (cupronickel and nickel silver)

Nitric acid - 20, acetic acid - 40, phosphoric acid - 40. Mixture temperature - 20 ° С, processing time - up to 2 minutes. The content of the components is in% (by weight).

Nitric acid - 30, acetic acid (glacial) - 70. Mixture temperature - 70 ... 80 ° С, processing time - 2 ... 3 s. Content of components - in% (by volume).

For aluminum and its alloys

Orthophosphoric acid - 75, sulfuric acid - 25. Mixture temperature - 100 ° С, processing time - 5 ... 10 minutes. The content of the components is in parts (by volume).

Phosphoric acid - 60, sulfuric acid - 200, nitric acid - 150, urea - 5g. Mixture temperature - 100 ° С, processing time - 20 s. The content of the components (except for urea) is in ml.

Orthophosphoric acid - 70, sulfuric acid - 22, boric acid - 8. Temperature of the mixture - 95 ° С, processing time - 5 ... 7 minutes. The content of the components is in parts (by volume).

Passivation

Passivation is the process of creating, by chemical means, an inert layer on the surface of a metal, which prevents the metal itself from being oxidized. The process of passivation of the surface of metal products is used by chasers when creating their works; craftsmen - in the manufacture of various crafts (chandeliers, sconces and other household items); sports anglers passivate their homemade metal baits.

Compositions of solutions for passivation (g / l)

For ferrous metals

Sodium nitrite - 40.100. Solution temperature - 30 ... 40 ° С, processing time - 15 ... 20 minutes.

Sodium nitrite - 10 ... 15, soda ash - 3 ... 7. Solution temperature - 70 ... 80 ° С, processing time - 2 ... 3 minutes.

Sodium nitrite - 2 ... 3, soda ash - 10, preparation OP-7 - 1 ... 2. Solution temperature - 40 ... 60 ° С, processing time - 10 ... 15 minutes.

Chromic anhydride - 50. Solution temperature - 65 ... 75 "С, processing time - 10 ... 20 minutes.

For copper and its alloys

Sulfuric acid - 15, potassium dichromate - 100. Solution temperature - 45 ° С, processing time - 5 ... 10 minutes.

Potassium dichromate - 150. Solution temperature - 60 ° С, processing time - 2 ... 5 minutes.

For aluminum and its alloys

Orthophosphoric acid - 300, chromic anhydride - 15. Solution temperature - 18 ... 25 ° С, processing time - 2 ... 5 minutes.

Potassium dichromate - 200. Solution temperature - 20 ° С, “processing time -5 ... 10 minutes.

For silver

Potassium dichromate - 50. Solution temperature - 25 ... 40 ° С, processing time - 20 minutes.

For zinc

Sulfuric acid - 2 ... 3, chromic anhydride - 150 ... 200. Solution temperature - 20 ° С, processing time - 5 ... 10 s.

Phosphating

As already said, phosphate film on the surface of steel parts is a fairly reliable anti-corrosion coating. It is also an excellent primer for paints and varnishes.

Some low temperature methods phosphating are applicable for the treatment of bodies passenger cars before coating them with anti-corrosion and anti-wear compounds.

Compositions of solutions for phosphating (g / l)

For steel

Majef (phosphate salts of manganese and iron) - 30, zinc nitrate - 40, sodium fluoride - 10. Solution temperature - 20 ° C, processing time - 40 minutes.

Monozinc phosphate - 75, zinc nitrate - 400 ... 600. Solution temperature - 20 ° С, processing time - 20 ... 30 s.

Mazhef - 25, zinc nitrate - 35, sodium nitrite - 3. Solution temperature - 20 ° С, processing time - 40 minutes.

Monoammonium phosphate - 300. Solution temperature - 60 ... 80 ° С, processing time - 20 ... 30 s.

Orthophosphoric acid - 60 ... 80, chromic anhydride - 100 ... 150. Solution temperature - 50 ... 60 ° С, processing time - 20 ... 30 minutes.

Orthophosphoric acid - 400 ... 550, butyl alcohol - 30. Solution temperature - 50 ° С, processing time - 20 minutes.

Application metal coatings

Chemical coating of some metals with others impresses with its simplicity technological process... Indeed, if, for example, it is necessary to chemically unnickel any steel part, it is enough to have a suitable enamel cookware, a heating source ( gas stove, stove stove, etc.) and relatively scarce chemical reagents. An hour or two - and the part is covered with a shiny nickel layer.

Note that only with the help of chemical nickel plating can you reliably nickel parts complex profile, internal cavities (pipes, etc.). True, chemical nickel plating (and some other similar processes) is not without its drawbacks. The main one is not too strong adhesion of the nickel film to the base metal. However, this drawback can be eliminated; for this, the so-called low-temperature diffusion method is used. It can significantly increase the adhesion of the nickel film to the base metal. This method is applicable for all chemical coatings of some metals with others.

Nickel plating

The process of chemical nickel plating is based on the reduction of nickel from aqueous solutions of its salts using sodium hypophosphite and some other chemical reagents.

Nickel coatings obtained by chemical means have an amorphous structure. The presence of phosphorus in nickel makes the film similar in hardness to a chromium film. Unfortunately, the adhesion of the nickel film to the base metal is comparatively low. Heat treatment of nickel films (low-temperature diffusion) consists in heating the nickel-plated parts to a temperature of 400 ° C and keeping them at this temperature for 1 h.

If the parts covered with nickel are hardened (springs, knives, fishhooks, etc.), then at a temperature of 40 ° C they can let go, that is, lose their main quality - hardness. In this case, low-temperature diffusion is carried out at a temperature of 270 ... 300 C with holding up to 3 hours. In this case, heat treatment also increases the hardness of the nickel coating.

All the listed advantages of chemical nickel plating have not escaped the attention of technologists. They found practical use for them (except for the use of decorative and anti-corrosion properties). So, with the help of chemical nickel plating, the axes of various mechanisms, worms of threading machines, etc. are repaired.

At home, using nickel plating (of course, chemical!) You can repair parts of various household devices. The technology here is extremely simple. For example, the axis of a device was demolished. Then build up (with excess) a layer of nickel on the damaged area. Then the working section of the axis is polished, bringing it to the desired size.

It should be noted that metals such as tin, lead, cadmium, zinc, bismuth and antimony cannot be coated with Chemical Nickel Plating.
Solutions used for chemical nickel plating are subdivided into acidic (pH - 4 ... 6.5) and alkaline (pH - above 6.5). Acidic solutions are preferable for coating ferrous metals, copper and brass. Alkaline - for stainless steels.

Acid solutions (in comparison with alkaline ones) on a polished part give a smoother (mirror-like) surface, they have lower porosity, and the rate of the process is higher. Another important feature of acidic solutions: they are less likely to self-discharge when the operating temperature is exceeded. (Self-discharge is the instantaneous precipitation of nickel into the solution with the splashing of the latter.)

The main advantage of alkaline solutions is a more reliable adhesion of the nickel film to the base metal.

And the last thing. Water for nickel plating (and when applying other coatings) is taken distilled (you can use condensate from household refrigerators). Chemical reagents are suitable at least clean (designation on the label - CH).

Before covering parts with any metal film, it is necessary to carry out special preparation of their surface.

The preparation of all metals and alloys is as follows. The processed part is degreased in one of the aqueous solutions, and then the part is pickled in one of the solutions listed below.

Compositions of solutions for pickling (g / l)

For steel

Sulfuric acid - 30 ... 50. Solution temperature - 20 ° С, processing time - 20 ... 60 s.

Hydrochloric acid - 20 ... 45. Solution temperature - 20 ° С, processing time - 15 ... 40 s.

Sulfuric acid - 50 ... 80, hydrochloric acid - 20 ... 30. Solution temperature - 20 ° С, processing time - 8 ... 10 s.

For copper and its alloys

Sulfuric acid - 5% solution. Temperature - 20 ° С, processing time - 20s.

For aluminum and its alloys

Nitric acid. (Attention, 10 ... 15% solution.) Solution temperature - 20 ° С, processing time - 5 ... 15 s.

Please note that for aluminum and its alloys, before chemical nickel plating, one more treatment is carried out - the so-called zincate. Below are solutions for zincate treatment.

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20 C, processing time - З ... 5s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20 ° C, processing time - 1.5 ... 2 minutes.

When preparing both solutions, first, caustic soda is dissolved in half of the water separately, and the zinc component in the other half. Then both solutions are poured together.

For cast aluminum alloys

Caustic soda - 10, zinc oxide - 5, Rochelle salt (crystalline hydrate) - 10. Solution temperature - 20 C, processing time - 2 minutes.

For wrought aluminum alloys

Ferric chloride (crystalline hydrate) - 1, sodium hydroxide - 525, zinc oxide 100, Rochelle salt - 10. Solution temperature - 25 ° C, processing time - 30 ... 60 s.

After zincate treatment, the parts are washed in water and hung in a nickel plating solution.

All nickel plating solutions are universal, that is, they are suitable for all metals (although there are some specific features). They are cooked in a specific sequence. So, all chemical reagents (except sodium hypophosphite) are dissolved in water (enameled dishes!). Then the solution is heated to operating temperature and only after that sodium hypophosphite is dissolved and the parts are hung in the solution.

In 1 liter of solution, a surface area of up to 2 dm2 can be nickel-free.

Compositions of solutions for nickel plating (g / l)

Nickel sulfate - 25, sodium succinate - 15, sodium hypophosphite - 30. Solution temperature - 90 ° С, pH - 4.5, film growth rate - 15 ... 20 μm / h.

Nickel chloride - 25, sodium succinic acid - 15, sodium hypophosphite - 30. Solution temperature - 90 ... 92 ° С, pH - 5.5, growth rate - 18 ... 25 μm / h.

Nickel chloride - 30, glycolic acid - 39, sodium hypophosphite - 10. Solution temperature 85, .. 89 ° С, pH - 4.2, growth rate - 15 ... 20 μm / h.

Nickel chloride - 21, sodium acetate - 10, sodium hypophosphite - 24, solution temperature - 97 ° С, pH - 5.2, growth rate - up to 60 μm / h.

Nickel sulfate - 21, sodium acetate - 10, lead sulfide - 20, sodium hypophosphite - 24. Solution temperature - 90 ° С, pH - 5, growth rate - up to 90 μm / h.

Nickel chloride - 30, acetic acid - 15, lead sulfide - 10 ... 15, sodium hypophosphite - 15. Solution temperature - 85 ... 87 ° С, pH - 4.5, growth rate - 12 ... 15 microns / h

Nickel chloride - 45, ammonium chloride - 45, sodium citrate - 45, sodium hypophosphite - 20. Solution temperature - 90 ° C, pH - 8.5, growth rate - 18 ... 20 μm / h.

Nickel chloride - 30, ammonium chloride - 30, sodium succinate - 100, ammonia (25% solution - 35, sodium hypophosphite - 25).
Temperature - 90 ° С, pH - 8 ... 8.5, growth rate - 8 ... 12 μm / h.

Nickel chloride - 45, ammonium chloride - 45, sodium acetate - 45, sodium hypophosphite - 20. Solution temperature - 88 ... 90 ° С, pH - 8 ... 9, growth rate - 18 ... 20 μm / h.

Nickel sulfate - 30, ammonium sulfate - 30, sodium hypophosphite - 10. Solution temperature - 85 ° С, pH - 8.2 ... 8.5, growth rate - 15 ... 18 μm / h.

Attention! According to existing GOSTs, a single-layer nickel coating per 1 cm2 has several dozen through (up to the base metal) pores. Naturally, in the open air, a steel part coated with nickel will quickly become covered with a "rash" of rust.

In a modern car, for example, the bumper is covered with a double layer (copper sublayer, and chrome on top) and even a triple layer (copper - nickel - chrome). But this does not save the part from rust, since according to GOST and the triple coating has several pores per 1 cm2. What to do? The way out is in the treatment of the coating surface with special compounds that close the pores.

Wipe the part with nickel (or other) coating with a slurry of magnesium oxide and water and immediately lower it for 1 ... 2 minutes in a 50% hydrochloric acid solution.

After heat treatment, the part that has not yet cooled down should be lowered into non-vitaminized fish oil (preferably old, unusable for its intended purpose).

Wipe the nickel-plated surface of the part 2 ... 3 times with LPS (easily penetrating grease).

In the last two cases, excess fat (grease) is removed from the surface with gasoline in a day.

The processing of fish oil on large surfaces (bumpers, car moldings) is carried out as follows. In hot weather, rub them with fish oil twice with a break of 12 ... 14 hours. Then, after 2 days, excess fat is removed with gasoline.

The following example characterizes the effectiveness of such processing. Nickel-plated fishing hooks start to rust immediately after the first fishing trip at sea. The same hooks treated with fish oil do not corrode almost all summer season sea fishing.

Chrome plating

Chemical chromium plating allows you to obtain a coating on the surface of metal parts gray which, after polishing, acquires the desired shine. Chromium adheres well to nickel plating. The presence of phosphorus in chemically obtained chromium significantly increases its hardness. Heat treatment for chrome coatings is necessary.

The following are proven recipes for chemical chromium plating.

Compositions of solutions for chemical chromium plating (g / l)

Chromium fluoride - 14, sodium citrate - 7, acetic acid - 10 ml, sodium hypophosphite - 7. Solution temperature - 85 ... 90 ° С, pH - 8 ... 11, growth rate - 1.0 ... 2 , 5 μm / h.

Chromium fluoride - 16, chromium chloride - 1, sodium acetate - 10, sodium oxalate - 4.5, sodium hypophosphite - 10. Solution temperature - 75 ... 90 ° С, pH - 4 ... 6, growth rate - 2 ... 2.5 μm / h.

Chromium fluoride - 17, chromium chloride - 1.2, sodium citrate - 8.5, sodium hypophosphite - 8.5. Solution temperature - 85 ... 90 ° С, pH - 8 ... 11, growth rate - 1 ... 2.5 μm / h.

Chromium acetate - 30, nickel acetate - 1, sodium glycolic acid - 40, sodium acetate - 20, sodium citrate - 40, acetic acid - 14 ml, sodium hydroxide - 14, sodium hypophosphite - 15. Solution temperature - 99 ° С, pH - 4 ... 6, the growth rate is up to 2.5 μm / h.

Chromium fluoride - 5 ... 10, chromium chloride - 5 ... 10, sodium citrate - 20 ... 30, sodium pyrophosphate (replacement of sodium hypophosphite) - 50 ... 75.
Solution temperature - 100 ° С, pH - 7.5 ... 9, growth rate - 2 ... 2.5 μm / h.

Boronickelation

The film of this double alloy has increased hardness (especially after heat treatment), high temperature melting, great wear resistance and significant corrosion resistance. All this allows the use of such a coating in various responsible homemade constructions... Below are the recipes for solutions in which boron-nickel treatment is carried out.

Compositions of solutions for chemical boron-nickel plating (g / l)

Nickel chloride - 20, sodium hydroxide - 40, ammonia (25% solution): - 11, sodium borohydride - 0.7, ethylenediamine (98% solution) - 4.5. Solution temperature - 97 ° С, growth rate - 10 μm / h.

Nickel sulfate - 30, triethylstetramine - 0.9, sodium hydroxide - 40, ammonia (25% solution) - 13, sodium borohydride - 1. Solution temperature - 97 C, growth rate - 2.5 μm / h.

Nickel chloride - 20, sodium hydroxide - 40, Rochelle salt - 65, ammonia (25% solution) - 13, sodium borohydride - 0.7. Solution temperature - 97 ° С, growth rate - 1.5 μm / h.

Caustic soda - 4 ... 40, potassium metabisulfite - 1 ... 1.5, sodium potassium tartrate - 30 ... 35, nickel chloride - 10 ... 30, ethylenediamine (50% solution) - 10 ... 30 , sodium borohydride - 0.6 ... 1.2. Solution temperature - 40 ... 60 ° С, growth rate - up to 30 μm / h.

The solutions are prepared in the same way as for nickel plating: first, everything is dissolved except sodium borohydride, the solution is heated and sodium borohydride is dissolved.

Borocobalting

The use of this chemical process makes it possible to obtain a film of especially high hardness. It is used for the repair of friction pairs where increased wear resistance of the coating is required.

Compositions of solutions for boron-cobalting (g / l)

Cobalt chloride - 20, sodium hydroxide - 40, sodium citrate - 100, ethylenediamine - 60, ammonium chloride - 10, sodium borohydride - 1. Solution temperature - 60 ° C, pH - 14, growth rate - 1.5 .. .2.5 μm / h.

Cobalt acetic acid - 19, ammonia (25% solution) - 250, tartaric acid potassium - 56, sodium borohydride - 8.3. Solution temperature - 50 ° С, pH - 12.5, growth rate - 3 μm / h.

Cobalt sulfate - 180, boric acid - 25, dimethylborazane - 37. Solution temperature - 18 ° С, pH - 4, growth rate - 6 μm / h.

Cobalt chloride - 24, ethylenediamine - 24, dimethylborazane - 3.5. Solution temperature - 70 С, pH - 11, growth rate - 1 μm / h.

The solution is prepared in the same way as boron-nickel.

Cadmium

On the farm, it is often necessary to use fasteners coated with cadmium. This is especially true for parts that are operated in the open air.

It is noted that chemically obtained cadmium coatings adhere well to the base metal even without heat treatment.

Cadmium chloride - 50, ethylenediamine - 100. Cadmium must come into contact with the parts (suspension on a cadmium wire, small parts are sprinkled with cadmium powder). Solution temperature - 65 ° С, pH - 6 ... 9, growth rate - 4 μm / h.

Attention! Ethylenediamine is the last to dissolve in the solution (after heating).

Copper plating

Chemical copper plating is most often used in the manufacture of printed circuit boards for radio electronics, in electroplating, for metallization of plastics, for the double coating of some metals with others.

Compositions of solutions for copper plating (g / l)

Copper sulfate - 10, sulfuric acid - 10. Solution temperature - 15 ... 25 ° С, growth rate - 10 μm / h.

Potassium-sodium tartrate - 150, copper sulfate - 30, caustic soda - 80. Solution temperature - 15 ... 25 ° С, growth rate - 12 microns / h.

Copper sulfate - 10 ... 50, caustic soda - 10 ... 30, Rochelle salt 40 ... 70, formalin (40% solution) - 15 ... 25. Solution temperature - 20 ° С, growth rate - 10 μm / h.

Copper sulfate - 8 ... 50, sulfuric acid - 8 ... 50. Solution temperature - 20 ° С, growth rate - 8 μm / h.

Copper sulfate - 63, potassium tartrate - 115, sodium carbonate - 143. Solution temperature - 20 C, growth rate - 15 μm / h.

Copper sulfate - 80 ... 100, caustic soda - 80 .., 100, sodium carbonate - 25 ... 30, nickel chloride - 2 ... 4, Rochelle salt - 150 ... 180, formalin (40% - solution) - 30 ... 35. Solution temperature - 20 ° С, growth rate - 10 μm / h. This solution makes it possible to obtain films with a low nickel content.

Copper sulfate - 25 ... 35, sodium hydroxide - 30 ... 40, sodium carbonate - 20-30, Trilon B - 80 ... 90, formalin (40% solution) - 20 ... 25, rhodanine - 0.003 ... 0.005, iron-synergistic potassium (red blood salt) - 0.1 ... 0.15. Solution temperature - 18 ... 25 ° С, growth rate - 8 μm / h.

This solution is characterized by a high stability of operation over time and allows one to obtain thick copper films.

To improve the adhesion of the film to the base metal, use heat treatment the same as for nickel.

Silvering

Silver plating of metal surfaces is perhaps the most popular process among craftsmen, which they use in their work. There are dozens of examples. For example, restoring a layer of silver on cupronickel cutlery, silvering samovars and other household items.

For chasers, silvering together with chemical coloration of metal surfaces (which will be discussed below) is a way to increase the artistic value of chased paintings. Imagine a minted ancient warrior wearing silver-plated chain mail and a helmet.

The process itself chemical silvering can be carried out using solutions and pastes. The latter is preferable when processing large surfaces (for example, when silvering samovars or details of large chased paintings).

Composition of solutions for silvering (g / l)

Silver chloride - 7.5, ferrocyanide potassium - 120, potassium carbonate - 80. Working solution temperature - about 100 ° С. Processing time - until receipt required thickness a layer of silver.

Silver chloride - 10, sodium chloride - 20, acidic potassium tartrate - 20. Processing - in a boiling solution.

Silver chloride - 20, ferrocyanide potassium - 100, potassium carbonate - 100, ammonia (30% solution) - 100, sodium chloride - 40. Processing - in a boiling solution.

First, a paste is prepared from silver chloride - 30 g, tartaric acid - 250 g, sodium chloride - 1250, and everything is diluted with water until sour cream is thick. 10-15 g of paste is dissolved in 1 liter of boiling water. Processing - in a boiling solution.

The parts are hung in silvering solutions on zinc wires (strips).

Processing time is determined visually. It should be noted here that brass is better silver than copper. A fairly thick layer of silver must be applied to the latter so that dark copper does not shine through the coating layer.

One more note. Solutions with silver salts cannot be stored for a long time, since explosive components may form. The same applies to all liquid pastes.

Compositions of paste for silvering.

In 300 ml warm water dissolve 2 g of a lapis pencil (sold in pharmacies, is a mixture of silver nitrate and amino acid potassium, taken in a ratio of 1: 2 (by weight). A 10% sodium chloride solution is gradually added to the resulting solution until the precipitation stops. silver chloride is filtered off and washed thoroughly in 5 ... 6 waters.

20 g of sodium thiosulfite are dissolved in 100 ml of water. Chlorine silver is added to the resulting solution until it stops dissolving. The solution is filtered and tooth powder is added to it until the consistency of liquid sour cream. With this paste, using a cotton swab, rub (silver) the part.

Lapis pencil - 15, lemon acid(food grade) - 55, ammonium chloride - 30. Each component is ground into powder before mixing. The content of the components is in% (by weight).

Silver chloride - 3, sodium chloride - 3, sodium carbonate - 6, chalk - 2. Content of components - in parts (by weight).

Silver chloride - 3, sodium chloride - 8, potassium tartrate - 8, chalk - 4. Content of components - in parts (by weight).

Silver nitrate - 1, sodium chloride - 2. Content of components - in parts (by weight).

The last four pastes are used as follows. The finely ground components are mixed. With a wet swab, dusting it with a dry mixture of chemical reagents, rub (silver) the desired part. The mixture is added all the time, constantly moistening the tampon.

When silvering aluminum and its alloys, the parts are first galvanized and then coated with silver.

The zincate treatment is carried out in one of the following solutions.

Compositions of solutions for zincate treatment (g / l)

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20 ° С, processing time - 3 ... 5 s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20 ° С, processing time - 1.5 ... 2.0 minutes. To obtain a solution, first dissolve sodium hydroxide in one half of the water, and zinc sulfate in the other. Then both solutions are poured together.

For duralumin

Caustic soda - 10, zinc oxide - 5, Rochelle salt - 10. Solution temperature - 20 ° C, processing time - 1 ... 2 minutes.

After zincate treatment, the parts are silver in any of the above solutions. However, the following solutions are considered the best (g / l).

Silver nitrate - 100, ammonium fluoride - 100. Solution temperature - 20 ° C.

Silver fluoride - 100, ammonium nitrate - 100. Solution temperature - 20 ° С.

Tinning

Chemical tinning of the surfaces of parts is used as an anti-corrosion coating and as a preliminary process (for aluminum and its alloys) before brazing. soft solders... Below are the compositions for tinning some metals.

Tinning compounds (g / l)

For steel

Tin chloride (fused) - 1, ammonia alum - 15. Tinning is carried out in a boiling solution, the growth rate is 5 ... 8 μm / h.

Tin chloride - 10, aluminum sulphate-ammonium - 300. Tinning is carried out in a boiling solution, the growth rate is 5 microns / h.

Tin chloride - 20, Rochelle salt - 10. Solution temperature - 80 ° С, growth rate - 3 ... 5 microns / h.

Tin chloride - 3 ... 4, Rochelle salt - until saturation. Solution temperature - 90 ... 100 ° С, growth rate - 4 ... 7 μm / h.

For copper and its alloys

Tin chloride - 1, potassium tartrate - 10. Tinning is carried out in a boiling solution, the growth rate is 10 μm / h.

Tin chloride - 20, lactic sodium - 200. Solution temperature - 20 ° С, growth rate - 10 microns / h.

Tin dichloride - 8, thiourea - 40 ... 45, sulfuric acid - 30 ... 40. Solution temperature - 20 ° С, growth rate - 15 μm / h.

Tin chloride - 8 ... 20, thiourea - 80 ... 90, hydrochloric acid - 6.5 ... 7.5, sodium chloride - 70 ... 80. Solution temperature - 50 ... 100 ° С, growth rate - 8 μm / h.

Tin chloride - 5.5, thiourea - 50, tartaric acid - 35. Solution temperature - 60 ... 70 ° С, growth rate - 5 ... 7 μm / h.

When tinning parts made of copper and its alloys, they are hung on zinc hangers. Small parts"Dust" with zinc sawdust.

For aluminum and its alloys

Tinning of aluminum and its alloys is preceded by some additional processes... First, parts defatted with acetone or B-70 gasoline are processed for 5 minutes at a temperature of 70 ° C of the following composition (g / l): sodium carbonate - 56, sodium phosphate - 56. Then the parts are lowered for 30 s in a 50% solution of nitrogen acids, rinsed thoroughly under running water and immediately placed in one of the solutions (for tinning) below.

Sodium stannate - 30, sodium hydroxide - 20. Solution temperature - 50 ... 60 ° С, growth rate - 4 μm / h.

Sodium stannate - 20 ... 80, potassium pyrophosphate - 30 ... 120, sodium hydroxide - 1.5 ... L, 7, ammonium oxalate - 10 ... 20. Solution temperature - 20 ... 40 ° С, growth rate - 5 μm / h.

Removing metal coatings

Usually this process is necessary to remove low-quality metal films or to clean any metal product being restored.

All of the solutions below work faster at elevated temperatures.

Compositions of solutions for removing metal coatings in parts (by volume)

For steel removing nickel from steel

Nitric acid - 2, sulfuric acid - 1, iron sulfate (oxide) - 5 ... 10. Mix temperature - 20 ° С.

Nitric acid - 8, water - 2. Solution temperature - 20 C.

Nitric acid - 7, acetic acid (glacial) - 3. Temperature of the mixture - 30 ° С.

For removing nickel from copper and its alloys (g / l)

Nitrobenzoic acid - 40 ... 75, sulfuric acid - 180. Solution temperature - 80 ... 90 C.

Nitrobenzoic acid - 35, ethylenediamine - 65, thiourea - 5 ... 7. Solution temperature - 20 ... 80 ° С.

To remove nickel from aluminum and its alloys, commercial nitric acid is used. The acid temperature is 50 ° C.

For removing copper from steel

Nitrobenzoic acid - 90, diethylenetriamine - 150, ammonium chloride - 50. Solution temperature - 80 ° C.

Sodium pyrosulfate - 70, ammonia (25% solution) - 330. Solution temperature - 60 °.

Sulfuric acid - 50, chromic anhydride - 500. Solution temperature - 20 ° С.

For removing copper from aluminum and its alloys (with zincate treatment)

Chromic anhydride - 480, sulfuric acid - 40. Solution temperature - 20 ... 70 ° С.

Technical nitric acid. Solution temperature - 50 ° С.

For removing silver from steel

Nitric acid - 50, sulfuric acid - 850. Temperature - 80 ° С.

Technical nitric acid. Temperature - 20 ° С.

Silver is removed from copper and its alloys with technical nitric acid. Temperature - 20 ° С.

Chromium is removed from steel with sodium hydroxide solution (200 g / l). Solution temperature - 20 C.

Chromium is removed from copper and its alloys with 10% hydrochloric acid. Solution temperature - 20 ° С.

Zinc is removed from steel with 10% hydrochloric acid - 200 g / l. Solution temperature - 20 ° С.

Zinc is removed from copper and its alloys with concentrated sulfuric acid. Temperature - 20 C.

Cadmium and zinc are removed from any metals with a solution of aluminum nitrate (120 g / l). Solution temperature - 20 ° С.

Tin is removed from steel with a solution containing sodium hydroxide - 120, nitrobenzoic acid - 30. Solution temperature - 20 ° C.

Tin is removed from copper and its alloys in a solution of ferric chloride - 75 ... 100, copper sulfate - 135 ... 160, acetic acid (glacial) - 175. Solution temperature - 20 ° C.

Chemical oxidation and coloring of metals

Chemical oxidation and painting of the surface of metal parts are intended to create an anti-corrosion coating on the surface of parts and enhance the decorative effect of the coating.

In ancient times, people already knew how to oxidize their crafts, changing their color (blackening silver, coloring gold, etc.), blackening steel objects (heating a steel part to 220 ... 325 ° C, they lubricated it with hemp oil).

Compositions of solutions for oxidizing and coloring steel (g / l)

Note that before oxidation, the part is ground or polished, degreased and pickled.

Black color

Caustic soda - 750, sodium nitrate - 175. Solution temperature - 135 ° С, processing time - 90 minutes. The film is dense, shiny.

Caustic soda - 500, sodium nitrate - 500. Solution temperature - 140 ° С, processing time - 9 minutes. The film is intense.

Caustic soda - 1500, sodium nitrate - 30. Solution temperature - 150 ° С, processing time - 10 minutes. The film is matte.

Caustic soda - 750, sodium nitrate - 225, sodium nitrate - 60. Solution temperature - 140 ° С, processing time - 90 minutes. The film is shiny.

Calcium nitrate - 30, phosphoric acid - 1, manganese peroxide - 1. Solution temperature - 100 ° С, processing time - 45 minutes. The film is matte.

All the above methods are characterized by a high working temperature of solutions, which, of course, does not allow processing large-sized parts. However, there is one "low-temperature solution" suitable for this business (g / l): sodium thiosulfate - 80, ammonium chloride - 60, phosphoric acid - 7, nitric acid - 3. Solution temperature - 20 ° C, processing time - 60 min ... The film is black, matte.

After oxidation (blackening) of steel parts, they are treated for 15 minutes in a solution of potassium chromium peak (120 g / l) at a temperature of 60 ° C.

The parts are then washed, dried and coated with any neutral machine oil.

Blue

Hydrochloric acid - 30, ferric chloride - 30, mercury nitrate - 30, ethyl alcohol - 120. Solution temperature - 20 ... 25 ° С, processing time - up to 12 hours.

Sodium hydrosulfide - 120, lead acetate - 30. Solution temperature - 90 ... 100 ° С, processing time - 20 ... 30 minutes.

Blue color

Lead acetic acid - 15 ... 20, sodium thiosulfate - 60, acetic acid (glacial) - 15 ... 30. Solution temperature - 80 ° С. The processing time depends on the color intensity.

Compositions of solutions for oxidizing and coloring copper (g / l)

Bluish black colors

Caustic soda - 600 ... 650, sodium nitrate - 100 ... 200. Solution temperature - 140 ° С, processing time - 2 hours.

Caustic soda - 550, sodium nitrate - 150 ... 200. Solution temperature - 135 ... 140 ° С, processing time - 15 ... 40 minutes.

Caustic soda - 700 ... 800, sodium nitrate - 200 ... 250, sodium nitrate -50 ... 70. Solution temperature - 140 ... 150 ° С, processing time - 15 ... 60 minutes.

Caustic soda - 50 ... 60, potassium persulfate - 14 ... 16. Solution temperature - 60 ... 65 С, processing time - 5 ... 8 minutes.

Potassium sulphide - 150. Solution temperature - 30 ° С, processing time - 5 ... 7 minutes.

In addition to the above, a solution of the so-called sulfuric liver is used. Sulfuric liver is obtained by melting in an iron can for 10 ... 15 minutes (with stirring) 1 part (by weight) of sulfur with 2 parts of potassium carbonate (potash). The latter can be replaced with the same amount of sodium carbonate or caustic soda.

The glassy mass of sulfuric liver is poured onto an iron sheet, cooled and crushed to a powder. Store sulfuric liver in an airtight container.

A solution of sulfuric liver is prepared in an enamel bowl at the rate of 30 ... 150 g / l, the temperature of the solution is 25 ... 100 ° C, the processing time is determined visually.

With a solution of sulfuric liver, in addition to copper, silver can be blackened well and steel can be satisfactorily blackened.

Green color

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 15 ... 25 ° С. The color intensity is determined visually.

Brown color

Potassium chloride - 45, nickel sulfate - 20, copper sulfate - 100. Solution temperature - 90 ... 100 ° С, color intensity is determined visually.

Brownish yellow color

Caustic soda - 50, potassium persulfate - 8. Solution temperature - 100 ° C, processing time - 5 ... 20 minutes.

Blue

Sodium thiosulfate - 160, lead acetate - 40. Solution temperature - 40 ... 100 ° С, processing time - up to 10 minutes.

Compositions for oxidizing and coloring brass (g / l)

Black color

Copper carbonate - 200, ammonia (25% solution) - 100. Solution temperature - 30 ... 40 ° С, processing time - 2 ... 5 minutes.

Bicarbonate copper - 60, ammonia (25% solution) - 500, brass (sawdust) - 0.5. Solution temperature - 60 ... 80 ° С, processing time - up to 30 minutes.

Brown color

Potassium chloride - 45, nickel sulfate - 20, copper sulfate - 105. Solution temperature - 90 ... 100 ° С, processing time - up to 10 minutes.

Copper sulfate - 50, sodium thiosulfate - 50. Solution temperature - 60 ... 80 ° С, processing time - up to 20 minutes.

Sodium sulfate - 100. Solution temperature - 70 ° С, processing time - up to 20 minutes.

Copper sulfate - 50, potassium permanganate - 5. Solution temperature - 18 ... 25 ° С, processing time - up to 60 minutes.

Blue

Lead acetic acid - 20, sodium thiosulfate - 60, acetic acid (essence) - 30. Solution temperature - 80 ° С, processing time - 7 minutes.

Green color

Nickel-ammonium sulfate - 60, sodium thiosulfate - 60. Solution temperature - 70 ... 75 ° С, processing time - up to 20 minutes.

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 20 ° C, processing time - up to 60 minutes.

Compositions for oxidation and coloring of bronze (g / l)

Green color

Ammonium chloride - 30, 5% acetic acid - 15, medium acetic copper salt - 5. Solution temperature - 25 ... 40 ° С. Hereinafter, the intensity of the bronze color is determined visually.

Ammonium chloride - 16, acidic potassium oxalate - 4.5% acetic acid - 1. Solution temperature - 25 ... 60 ° С.

Copper nitrate - 10, ammonium chloride - 10, zinc chloride - 10. Solution temperature - 18 ... 25 ° С.

Yellow-green color

Copper nitrate - 200, sodium chloride - 20. Solution temperature - 25 ° С.

Blue to yellow-green

Depending on the processing time, it is possible to obtain colors from blue to yellow-green in a solution containing ammonium carbonate - 250, ammonium chloride - 250. Solution temperature - 18 ... 25 ° С.

Patination (giving the appearance old bronze) is carried out in such a solution: sulfuric liver - 25, ammonia (25% solution) - 10. The temperature of the solution is 18 ... 25 ° С.

Compositions for oxidizing and dyeing silver (g / l)

Black color

Sulfuric liver - 20 ... 80. Solution temperature - 60, 70 ° C. Hereinafter, the color intensity is determined visually.

Ammonium carbonate - 10, potassium sulphide - 25. Solution temperature - 40 ... 60 ° С.

Potassium sulfate - 10. Solution temperature - 60 ° С.

Copper sulfate - 2, ammonium nitrate - 1, ammonia (5% solution) - 2, acetic acid (essence) - 10. Solution temperature - 25 ... 40 ° С. The content of the components in this solution is given in parts (by weight).

Brown color

Ammonium sulfate solution - 20 g / l. Solution temperature - 60 ... 80 ° С.

Copper sulfate - 10, ammonia (5% solution) - 5, acetic acid - 100. Solution temperature - 30 ... 60 ° C. The content of the components in the solution is in parts (by weight).

Copper sulfate - 100, 5% acetic acid - 100, ammonium chloride - 5. Solution temperature - 40 ... 60 ° С. The content of the components in the solution is in parts (by weight).

Copper sulfate - 20, potassium nitrate - 10, ammonium chloride - 20, 5% acetic acid - 100. Solution temperature - 25 ... 40 ° C. The content of the components in the solution is in parts (by weight).

Blue

Sulfuric liver - 1.5, ammonium carbonate - 10. Solution temperature - 60 ° С.

Sulfuric liver - 15, ammonium chloride - 40. Solution temperature - 40 ... 60 ° С.

Green color

Iodine - 100, hydrochloric acid - 300. Solution temperature - 20 ° С.

Iodine - 11.5, potassium iodide - 11.5. Solution temperature - 20 ° С.

Attention! When dyeing silver green, work in the dark!

Composition for oxidizing and coloring nickel (g / l)

Nickel can only be dyed black. The solution (g / l) contains: ammonium persulfate - 200, sodium sulfate - 100, iron sulfate - 9, thiocyanate ammonium - 6. Solution temperature - 20 ... 25 ° С, processing time - 1-2 minutes.

Compositions for the oxidation of aluminum and its alloys (g / l)

Black color

Ammonium molybdate - 10 ... 20, ammonium chloride - 5 ... 15. Solution temperature - 90 ... 100 ° С, processing time - 2 ... 10 minutes.

Grey colour

Arsenic trioxide - 70 ... 75, sodium carbonate - 70 ... 75. Solution temperature - boiling, processing time - 1 ... 2 minutes.

Green color

Orthophosphoric acid - 40 ... 50, acidic potassium fluoride - 3 ... 5, chromic anhydride - 5 ... 7. Solution temperature - 20 ... 40 С, processing time - 5 ... 7 minutes.

Orange color

Chromic anhydride - 3 ... 5, sodium fluorosilicate - 3 ... 5. Solution temperature - 20 ... 40 ° С, processing time - 8 ... 10 minutes.

Yellow-brown color

Sodium carbonate - 40 ... 50, sodium chloride - 10 ... 15, caustic soda - 2 ... 2.5. Solution temperature - 80 ... 100 ° С, processing time - 3 ... 20 minutes.

Protective compounds

Often, a craftsman needs to process (paint, cover with another metal, etc.) only part of the craft, and leave the rest of the surface unchanged.
For this, the surface that does not need to be covered is painted over with a protective compound that prevents the formation of a particular film.

The most affordable, but not heat-resistant, protective coatings are waxy substances (wax, stearin, paraffin, ceresin) dissolved in turpentine. To prepare such a coating, wax and turpentine are usually mixed in a ratio of 2: 9 (by weight). This composition is prepared as follows. In a water bath, the wax is melted and warm turpentine is introduced into it. To protective compound would be contrasting (its presence could be clearly seen, controlled), a small amount of a dark alcohol-soluble paint is introduced into the composition. If it is not available, it is not difficult to add a small amount of dark boot cream to the composition.

A more complex recipe can be cited,% (by weight): paraffin - 70, beeswax- 10, rosin - 10, pitch varnish (Kuzbasslak) - 10. All components are mixed, melted over low heat and mixed thoroughly.

Wax-like protective compounds are applied hot with a brush or swab. All of them are designed for an operating temperature not exceeding 70 ° C.
Somewhat better heat resistance (operating temperature up to 85 ° C) is possessed by protective compounds based on asphalt, bitumen and pitch varnishes. Usually they are liquefied with turpentine in a 1: 1 ratio (by weight). The cold composition is applied to the surface of the part with a brush or swab. Drying time - 12 ... 16 hours.

Perchlorovinyl paints, varnishes and enamels can withstand temperatures up to 95 ° C, oil-bitumen varnishes and enamels, asphalt-oil and bakelite varnishes - up to 120 ° C.

The most acid-resistant protective composition is a mixture of glue 88N (or "Moment") and filler (porcelain flour, talc, kaolin, chromium oxide), taken in the ratio: 1: 1 (by weight). The required viscosity is obtained by adding to the mixture a solvent consisting of 2 parts (by volume) of B-70 gasoline and 1 part of ethyl acetate (or butyl acetate). Working temperature of such a protective composition is up to 150 C.

A good protective composition is epoxy varnish (or putty). Working temperature - up to 160 ° С.

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