MOU Secondary school in the village of Novopavlovka
Petrovsk-Zabaykalsky district of Zabaikalsky Krai
Research work on the topic:
Why is the water rusty?
The work was done by a student of the 2nd grade
Ioninsky Dmitry,
Novopavlovka
INTRODUCTION | |
Theoretical part | |
What is rust | |
The role of metals in human life | |
Practical part | |
EXPERIENCE 1. "In what water do metals rust the fastest" | |
EXPERIENCE 2. "In what environment do metals rust the fastest" | |
EXPERIENCE 3. "How different metals resist corrosion" | |
CONCLUSION | |
LIST OF USED LITERATURE |
INTRODUCTION
I noticed that if the water is not pumped out of the well for some time, then it becomes yellowish in color. I was wondering why the water turns yellow? I learned from my dad that it was rust.
Goal of the work: find out why rust forms on iron, in which solutions rust forms and find out methods of rust protection.
To achieve this goal, it is necessary to solve a number of tasks:
Learn what rust is, why it occurs (theoretically).
· By experience, get rust on iron nails at home in various environments.
· Analyze and compare the results of observations of this experiment and draw conclusions.
Object of study: iron nail in test tubes with various solutions.
Research methods:
study of literature;
Observations
analysis of the obtained data;
generalization.
I put forward hypothesis: iron is destroyed, that is, it rusts, in any solutions.
To conduct this study, my teacher Lyudmila Sergeevna and I studied special literature (authors are listed in the list of references). With the participation of my family, I set up experiments, observed, analyzed and drew conclusions.
MAIN CONTENT
Theoretical part
What is rust
Initially, I read in Ozhegov's explanatory dictionary what is rust?
RZAVCHINA, - s, f.
1. A red-brown coating on iron, formed as a result of oxidation and leading to the destruction of the metal, as well as a trace on something. from such an attack. Some kind of river appeared in my soul.(trans.: something corrosive, tormenting).
2. Brown film on marsh water.
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Rust occurs when the atmosphere interacts with iron. The process of its formation is called rusting or corrosion. Corrosion is the spontaneous destruction of metals as a result of interaction with the environment. The rusting process of iron begins only when there is moisture in the air. When a drop of water hits the surface of an iron product, after a while, you can notice a change in its color. The drop becomes cloudy and gradually turns brown. This indicates the appearance of iron corrosion products at the point of contact of water with the surface.
The role of metals in human life
In everyday life, metals are used everywhere. We live in the world of metals. At home, on the street, on the bus - everywhere we are surrounded by metal objects. We simply cannot imagine our life without them.
Iron- chemical element, silver-white metal. In its pure form, it is practically not used because of its low strength. As a rule, iron-based alloys are used - steel and cast iron.
Steel is the most important type of iron alloys. It is distinguished from pure iron by a carbon content of less than 2%, but it is this minor addition that gives the alloy a hardness that iron does not have. The technical and economic level of development of the state depends to a large extent on how much steel is smelted in the country per capita.
Aluminum used in aircraft construction because it is very strong and light. Unlike iron, aluminum is not afraid of moisture and does not rust, so products made from it do not need protective coatings.
Zinc serves as an additive to copper, but it is often used in its pure form. Zinc has good casting qualities, so parts for various machines are cast from it. We usually see this bluish-white metal with a characteristic mottled pattern on new drainpipes and metal pails. All these products are made of the so-called roofing iron - mild sheet steel coated with a thin layer of zinc. It protects the base metal from rust. Such iron is called galvanized.
Copper it is very plastic and conducts electric current better than other metals (with the exception of precious silver). These qualities allow it to be used in electrical wires. Here it is considered the number one metal.
Silver. Ancient casters, blacksmiths and jewelers valued this metal for its softness and pliability in processing. From the time of ancient Greece until the beginning of this century, most of the mined silver went to the minting of coins, and the rest to the manufacture of jewelry, cutlery and utensils. Today, silver is also valued for the fact that it conducts electricity better than any metal. Therefore, it is widely used in electrical engineering. A lot of silver goes to the manufacture of batteries, but even more - to the production of photographs and film materials. The metal has one more advantage: it kills pathogenic microbes. Therefore, drugs are prepared on its basis, with which purulent wounds are washed, bactericidal paper impregnated with silver compounds is applied to the body to heal small wounds. Silver is also used in mirror factories.
Iron-based alloys suffer the most from corrosion. “Rust eats iron” is an old but true saying. About 10% of the mined metal is lost forever. Corrosion is followed by erosion - the destruction of metal products. After that, the metal is no longer suitable. And yet, 2/3 of the metals are returned to production after being remelted in open-hearth furnaces. That's why it's important to collect scrap metal.
I decided to experiment with iron nails by placing them in various environments.
Practical part
EXPERIENCE 1. In which water do metals rust the fastest?
Purpose of experience: find out in which water iron rusts the fastest
I took water from 4 sources (from a well, from a river, distilled, snow) and put identical iron nails into it. Banks with water were in the same conditions. After 2 days, the water turned yellow, after a week, rust appeared on the nails, after a month, the rust layer grew significantly. Rust formed on all nails, regardless of the source of water they were in.
Well water | Water from the river | Distilled water | ||
Put the nails in the water |
||||
The water turned yellow | The water turned yellow | The water turned yellow | The water turned yellow |
|
Rust on the nail | Rust on the nail | Rust on the nail | Rust on the nail |
|
The layer of rust is growing | The layer of rust is growing | The layer of rust is growing | The layer of rust is growing |
Conclusion: rust forms on iron in any water.
EXPERIENCE 2. "In what environment do metals rust the fastest"
Target experience: find out in which environment iron rusts the fastest
I decided to find out in which environment iron rusts the fastest. To do this, took 4 cans of water from the well. I added salt to the first, sugar to the second, soda to the third, and vinegar to the fourth. In each jar lowered an iron nail.
After 2 days:
a small yellow precipitate appeared in the water with salt, the solution itself remained transparent;
the solution with sugar turned yellow;
A solution with transparent vinegar on the walls of the jar bubbles.
A month later:
a layer of rust and salt crystals on the nail appeared in the water with salt;
The solution with sugar has brightened, there is no rust;
There were no changes in water with soda;
Vinegar solution is dark brown, at the bottom of the jar there are particles of a nail.
Water with sugar | Salt water | Water with soda | Water with vinegar |
|
Put the nails in different solutions |
||||
The solution turned yellow | Small yellow precipitate, clear solution | No changes | The solution is transparent, there are bubbles on the walls of the jar |
|
The solution brightened, there is no rust | A layer of rust and salt crystals appeared on the nail | No changes | The solution is dark brown, at the bottom of the jar there are particles of a nail |
Conclusion: rust does not form in an alkaline environment; in an acidic environment, iron is destroyed.
EXPERIENCE 3 . "How Different Metals Resist Corrosion"
Purpose of experience: find out if rust forms on other metals
I wanted to find out if rust forms on other metals. I took 4 different metals (copper, aluminium, zinc, iron) and put them in water. Separately put a painted iron nail into the water. After 2 days, water with iron became rusty, and rust did not form on other metals even after a month. Water with a painted nail did not rust.
Conclusion: rust is formed only when water interacts with iron.
CONCLUSION
In the course of my research, I tried to find out why rust forms on iron, in what solutions rust forms, and to find out methods for protecting against rust. The example of the study shows that water is a favorable environment for the occurrence of rust, no matter what source it comes from. An alkaline environment is favorable for protecting iron from rust. In an acidic environment, iron breaks down more quickly. Iron can be preserved if it is not allowed to come into contact with water, for this it is necessary to carry out staining.
LIST OF USED LITERATURE
2. Big encyclopedia "Why". - M.: "ROSMEN", 2006
3. I know the world. AST, 1999
Why does iron rust?
If you leave an iron object in a damp and damp place for several days, it will rust, as if it had been painted with reddish paint.
What is rust? Why does it form on iron and steel objects? Rust is iron oxide. It is formed as a result of the "combustion" of iron when combined with oxygen dissolved in water.
This means that in the absence of moisture and water in the air, there is no oxygen dissolved in water at all and rust does not form.
If a raindrop falls on a shiny iron surface, it remains transparent for a short period of time. Iron and oxygen in the water begin to interact and form an oxide, that is, rust, inside the drop. The water becomes reddish and the rust floats in the water as small particles. When the drop evaporates, rust remains, forming a reddish layer on the surface of the iron.
If rust has already appeared, it will grow in dry air. This is because the porous rust patch absorbs the moisture in the air - it attracts and holds it. This is why it is easier to prevent rust than to stop it once it has appeared. The problem of rust prevention is very important, since iron and steel products must be stored for a long time. Sometimes they are covered with a layer of paint or plastic. What would you do to keep warships from rusting when not in use? This problem is solved with the help of moisture absorbers. Such mechanisms replace moist air in compartments with dry air. Rust in such conditions can not appear!
If you leave an iron object in a damp and damp place for several days, it will rust, as if it had been painted with reddish paint.
What is rust? Why does it form on iron and steel objects? Rust is iron oxide. It is formed as a result of the "combustion" of iron when combined with oxygen dissolved in water.
This means that in the absence of moisture and water in the air, there is no oxygen dissolved in water at all and rust does not form.
If a raindrop falls on a shiny iron surface, it remains transparent for a short period of time. Iron and oxygen in the water begin to interact and form an oxide, that is, rust, inside the drop. The water becomes reddish and the rust floats in the water as small particles. When the drop evaporates, rust remains, forming a reddish layer on the surface of the iron.
If rust has already appeared, it will grow in dry air. This is because the porous rust patch absorbs the moisture in the air - it attracts and holds it. This is why it is easier to prevent rust than to stop it once it has appeared. The problem of rust prevention is very important, since iron and steel products must be stored for a long time. Sometimes they are covered with a layer of paint or plastic. What would you do to keep warships from rusting when not in use? This problem is solved with the help of moisture absorbers. Such mechanisms replace moist air in compartments with dry air. Rust in such conditions can not appear!
Dangerous enemy - rust! No matter how strong the metal, rust will still overcome it. Hear about this one story. In ancient times, one unlucky king ordered a lot of various weapons to be hidden in the damp cellars of the fortress in reserve: steel swords, guns, cannons, cannonballs. Only he did not order to put gunpowder there, so that it would not become damp. And with iron, they say, nothing will happen. Fortunately, there was no war for a long time, and the weapons lay in the basement for many years.
The king gathered for war and ordered to arm the young recruits. Heavy doors were opened, battle swords were taken out of the basement - they look, but they are all rusty. They began to clean - the swords became thinner than kitchen knives. Where do these fit! They got the guns - they were also rusty. Of these, you shoot - they will burst in your hands. It's time for the guns. With cores. They began to rip off the rust from them. They cleaned it up so much that the kernels the size of a watermelon became smaller than a potato. How to load such guns? The guns are great for them now, not in size. I had to cancel my trip! Summed up dampness, moisture.
And this story happened recently. A tractor was walking on the ice and landed in a snow-covered wormwood. The tractor driver was saved, but the tractor sank. Only a year later they managed to lift a heavy car. I cleaned it of rust for a long time, but it was not possible to start the engine until many of its parts rusted in the water were replaced with new ones.
Where else does iron rust?
If only it would rust in water! But metal rusts even in a hot desert. Around - no matter how you look - you will not find a drop of water. But there are always tiny, completely invisible particles of moisture in the air. And this smallness is enough for the metal to gradually begin to rust. And in a damp climate, it, of course, collapses much faster.
How much iron does rust destroy? The answer is ready. In ten years, rust eats up as much metal as all the metallurgical plants in the world produce in a year. It turns out that rust eats millions of tons of metal! Here people have long declared war on her! How are you ? That's right, put on rubber boots and raincoats, and even better hide under the roof. The same is true with metal. Cars, machine tools are hidden under sheds, under the roofs of workshops.
Rust and metal corrosion protection
They lay a gas pipeline, an oil pipeline, a water pipeline - a waterproof raincoat is put on the pipes - they are wrapped with tarred cloth or paper.
What about cars? After all, they are not only painted with elegant, bright colors for beauty. Although the paint layer is thin, it protects well from dampness, and therefore from rust. For this, bridges, and wagons, and ships, and roofs are painted ...
But not only paint can protect the metal, iron can be covered with a thin layer of another, more resistant metal - zinc. And the roof immediately becomes more durable. Tin cans are also iron - tin. Here, a thin layer of molten tin is applied to the iron.
There are many other ways to protect metal from rust, and scientists are looking for new, more reliable ones.
What do a rusty nail, a rusted bridge, or a leaky iron fence have in common? Why do iron structures and iron products rust in general? What is rust exactly? We will try to answer these questions in our article. Consider the causes of rusting of metals and ways to protect against this natural phenomenon that is harmful to us.
Causes of rust
It all starts with metal mining. Not only iron, but also, for example, magnesium - is mined initially in the form of ore. Aluminum, manganese, iron, magnesium ores do not contain pure metals, but their chemical compounds: carbonates, oxides, sulfides, hydroxides.
These are chemical compounds of metals with carbon, oxygen, sulfur, water, etc. Pure metals in nature are once, twice and counted - platinum, gold, silver - noble metals - they are found in the form of metals in a free state, and do not strongly tend to the formation of chemical compounds.
However, most metals are still not free under natural conditions, and in order to release them from the original compounds, it is necessary to melt ores, thus reducing pure metals.
But by smelting metal-containing ore, although we get the metal in its pure form, this is still an unstable state, far from natural. For this reason, pure metal, under normal environmental conditions, tends to return back to its original state, that is, to oxidize, and this is metal corrosion.
Thus, corrosion is a natural destruction process for metals that occurs under conditions of their interaction with the environment. In particular, rusting is the process of formation of iron hydroxide Fe (OH) 3, which occurs in the presence of water.
But the natural fact plays into the hands of people that the oxidative reaction does not proceed very rapidly in the atmosphere familiar to us, it goes at a very low speed, so bridges and planes do not collapse instantly, and pots do not crumble before our eyes into a red powder. In addition, corrosion can, in principle, be slowed down by resorting to some traditional tricks.
For example, stainless steel does not rust, although it is composed of iron prone to oxidation, it nevertheless does not become coated with red hydroxide. The point here is that stainless steel is not pure iron, stainless steel is an alloy of iron and another metal, mainly chromium.
In addition to chromium, steel may contain nickel, molybdenum, titanium, niobium, sulfur, phosphorus, etc. The addition of additional elements to alloys that are responsible for certain properties of the resulting alloys is called alloying.
Ways to protect against corrosion
As we noted above, the main alloying element added to ordinary steel to give it anti-corrosion properties is chromium. Chromium oxidizes faster than iron, that is, it takes the hit. On the surface of stainless steel, therefore, first appears a protective film of chromium oxide, which is dark in color and not as loose as normal iron rust.
Chromium oxide does not allow aggressive ions from the environment harmful to iron to pass through, and the metal is protected from corrosion, like a strong sealed protective suit. That is, the oxide film in this case has a protective function.
The amount of chromium in stainless steel, as a rule, is not lower than 13%, stainless steel contains slightly less nickel, and other alloying additives are present in much smaller quantities.
It is thanks to the protective films that are the first to take on the impact of the environment that many metals are resistant to corrosion in various environments. For example, a spoon, plate or pan made of aluminum never shines very much; if you look closely, they have a whitish tint. This is just aluminum oxide, which is formed when pure aluminum comes into contact with air, and then protects the metal from corrosion.
An oxide film appears on its own, and if you clean an aluminum pan with sandpaper, then after a few seconds of shine the surface will become whitish again - the aluminum on the cleaned surface will oxidize again under the action of atmospheric oxygen.
Since the aluminum oxide film forms on it by itself, without special technological tricks, it is called a passive film. Such metals, on which an oxide film forms naturally, are called passivated. In particular, aluminum is a passivated metal.
Some metals are forcibly transferred to a passive state, for example, the highest iron oxide - Fe2O3 is able to protect iron and its alloys in air at high temperatures and even in water, which neither red hydroxide nor lower oxides of the same iron can boast of.
There are nuances in the phenomenon of passivation. For example, in strong sulfuric acid, instantly passivated steel is resistant to corrosion, and in a weak solution of sulfuric acid, corrosion will begin immediately.
Why is this happening? The answer to the apparent paradox is that in a strong acid, a passivating film instantly forms on the surface of stainless steel, since the acid of a higher concentration has pronounced oxidizing properties.
At the same time, a weak acid does not oxidize the steel fast enough, and a protective film does not form, just corrosion begins. In such cases, when the oxidizing medium is not sufficiently aggressive, in order to achieve the passivation effect, special chemical additives (inhibitors, corrosion inhibitors) are used to help form a passive film on the metal surface.
Since not all metals are prone to the formation of passive films on their surface, even forcibly, the addition of moderators to an oxidizing environment simply leads to preventive retention of the metal under reduction conditions, when oxidation is energetically suppressed, that is, in the presence of an additive in an aggressive environment, it turns out to be energetically unfavorable .
There is another way to keep the metal under reduction conditions, if it is not possible to use an inhibitor - to apply a more active coating: a galvanized bucket does not rust, since the zinc of the coating corrodes on contact with the environment ahead of the iron, that is, it takes a hit on itself, being a more active metal , zinc is more likely to enter into a chemical reaction.
The bottom of a ship is often protected in the same way: a piece of tread is attached to it, and then the tread is destroyed, and the bottom remains intact.
Electrochemical anti-corrosion protection of underground utilities is also a very common way to combat the formation of rust on them. Recovery conditions are created by applying a negative cathode potential to the metal, and in this mode, the metal oxidation process can no longer proceed simply energetically.
One might ask why the surfaces at risk of corrosion are simply not painted with paint, why not just enamel the part vulnerable to corrosion each time? Why are there different ways?
The answer is simple. Enamel can be damaged, for example, car paint can break off in an inconspicuous place, and the body will begin to gradually but continuously rust, since sulfur compounds, salts, water, air oxygen will flow to this place, and as a result, the body will collapse.
To prevent such a development of events, they resort to additional anti-corrosion treatment of the body. A car is not an enamel plate, which, if the enamel is damaged, can simply be thrown away and a new one can be bought.
Current state of affairs
Despite the apparent knowledge and elaboration of the phenomenon of corrosion, despite the versatile methods of protection used, corrosion still poses a certain danger. Pipelines are destroyed and this leads to oil and gas emissions, planes fall, trains crash. Nature is more complex than it might seem at first glance, and humanity still has many aspects of corrosion to explore.
Thus, even corrosion-resistant alloys are resistant only in certain predictable conditions for which they were originally intended. For example, stainless steels do not tolerate chlorides, and are affected by them - pitting, pitting and intercrystalline corrosion occur.
Outwardly, without a hint of rust, the structure can suddenly collapse if small, but very deep lesions form inside. Microcracks penetrating the thickness of the metal are invisible from the outside.
Even an alloy that is not subject to corrosion can suddenly crack when under prolonged mechanical stress - just a huge crack will suddenly destroy the structure. This has already happened around the world with metal building structures, machinery, and even airplanes and helicopters.
Andrey Povny