Aluminum is a material that people often use in industry and for their own needs. Such a metal is flexible, as well as resistant to external influences. It is non-toxic and safe for human he alth. Silver color allows the metal to be used for various purposes. This is industry and domestic sphere.
When working in industry, people often wonder if aluminum rusts. Everyone knows that if damage appears on the sheet, then corrosion can develop. You should find out why aluminum rusts differently than other alloys. It is necessary to find out the reasons why it corrodes. Read about all this and more in our today's article.
Properties
Let's study the characteristics of aluminum. The described metal melts at a temperature of 659 degrees Celsius. The density of the substance is 2.69103 kg/cm3. Aluminum belongs to the group of active metals. Corrosion resistancedepends on a number of factors:
- The purity of the alloy. For the production of various equipment, a metal is taken that is distinguished by its purity. It should not contain various impurities. Widespread aluminum brand AI1, as well as AB2.
- Aluminum environment.
- What is the concentration of impurities in the aluminum environment.
- Temperature.
- The pH of the environment has a great influence. You need to know that aluminum oxide can form when the pH is between 3 and 9. In an environment where an oxide film immediately appears on the surface of the aluminum sheet, corrosion processes will not develop.
How is aluminum protected from corrosion?
Alloys of other metals are prone to rust. It shows up fairly quickly. If you create certain conditions for aluminum, then it will not collapse for many years. To protect aluminum from corrosion, a special film is formed on it. It lays down a thin layer, which is from 3 to 30 nanometers. It consists of a similar coating of aluminum oxide.
The film is durable and gives the metal additional protection from external negative influences. Thanks to this layer, air and moisture do not enter the structure of the material. If the integrity of the oxide coating is violated, then the process of aluminum corrosion begins. The metal loses its properties.
Causes of corrosion
When it comes to the question of whether aluminum rusts, it is necessary to think about the causes that lead to corrosion. Various external factors canspeed up this process. Causes of rust on aluminum can be as follows:
- Interaction with any acid or alkali.
- Mechanical pressure. For example, friction or a strong impact, after which a scratch appears on the top layer of metal.
- There are industrial areas. In them, the decay products of the fuel affect the oxide film and destroy it. The metal starts to deteriorate. A similar situation occurs in megacities, where the decay products of the fuel will interact with sulfur, as well as with carbon oxides. A similar process destroys the film on aluminum. After this kind of external influence, aluminum corrodes.
- It should be remembered that chlorine, fluorine, as well as bromine and sodium can dissolve the protective layer of the metal.
- If building mixtures get on the metal, it starts to deteriorate quickly. In this case, aluminum is adversely affected by cement.
- Does water rust aluminum? If it gets on the sheet, then the metal may be subject to corrosion processes. It is important to clarify which liquid has an effect. Many use a special alloy that does not corrode from water. It is called duralumin. The unique alloy is used in conjunction with copper as well as manganese.
What is electrochemical corrosion and can it be on a sheet of aluminum?
Most often, the appearance of electrochemical corrosion is provoked by galvanic couples. Damage appears at the junction of two different alloys. In this case, rust will be clearly evident. An important pointis that only one metal deteriorates, and the second is the source of starting the corrosion process. In order not to be afraid of electrochemical corrosion, you need to use a magnesium alloy. Due to electrochemical rust, experts do not recommend using ordinary iron in contact with an aluminum body.
What factors can slow down the process?
There are a number of factors that slow down the process of aluminum corrosion, and some of them stop this phenomenon. The following are distinguished:
- In order for the anti-corrosion properties of aluminum to be preserved, it is necessary to maintain an acid-base balance. The range should be six to eight units.
- It is believed that pure metal, without impurities, better resists aggressive environments. Scientists have carried out experiments. According to the results, it can be said that pure aluminum alloys (90%) are more susceptible to corrosion than an alloy containing 99% of this substance. The first option corrodes 80 times faster than the second alloy.
- To ensure that the metal does not lose its properties longer in an aggressive environment, it is treated with a special paint. You can use a polymer composition. After processing, an additional protective layer appears.
- If you add 3% manganese to the alloy during production, it will be possible to avoid corrosion of aluminum.
Under what conditions begins the destruction of aluminum in air
Some people wonder if aluminum rusts in air. If the oxide film on the upperlayer of metal, the corrosion process may begin. As a result, rust may appear. Film growth tends to slow down in fresh air. It should be remembered that aluminum oxide has good adhesion to the metal surface.
If the sheet is kept in stock, then the film will be from 0.01 to 0.02 microns. If the metal is in contact with dry oxygen, then the thickness of the oxide film on the surface will be from 0.02 to 0.04 microns. If aluminum is subjected to heat treatment, the film thickness changes. It will be equal to 0.1 µm.
Aluminum is considered durable enough to be used outdoors. For example, it is used in rural areas, as well as in remote industrial areas.
How does water affect the described metal?
Corrosion of aluminum in water can occur from damage to the top layer and protective film. The high temperature of the liquid contributes to the rapid destruction of the metal. If aluminum is placed in fresh water, then corrosion processes will practically not be observed. If you increase the temperature of the water, then changes can not be noticed. When the liquid is heated to a temperature of 80 degrees and above, the metal begins to deteriorate.
The corrosion rate of aluminum increases if alkali enters the water. The described metal is highly sensitive to s alt. That is why sea water is destructive for him. To use this metal in sea water, it is necessary to add magnesium or silicon to the liquid. If you use an aluminum sheet, in the compositionwhich has copper, then the corrosion of the alloy will proceed much faster than that of a pure substance.
Is sulfuric acid dangerous for aluminum?
People wonder if aluminum rusts in sulfuric acid. Such an acid is potentially hazardous to alloys. It has pronounced oxidizing properties. They destroy the oxide film and accelerate the corrosion of the metal.
An interesting point is that concentrated cold sulfur does not affect aluminum. If aluminum is heated, then metal corrosion processes can begin. In this case, a s alt appears, it is called aluminum sulfate. It is soluble in water.
Resistance of aluminum in nitric acid
The described metal is characterized by increased resistance when it enters a solution of nitric acid. It is often synthesized to make concentrated nitric acid.
Which substances do not affect aluminum?
Do not be afraid of corrosion processes if aluminum comes into contact with citric acid. Malic acid and fruit juice will not change the properties of its alloy either. Oil has little effect on alloys containing aluminum.
Will metal corrode in contact with alkali?
Do not allow aluminum to come into contact with various alkalis. They easily destroy the protective film on the top layer. The metal reacts with water, after which hydrogen begins to be released. The process of corrosion occurs in this case quickly. Mercury and copper are also detrimental to the protective layer of aluminum.
So we found out if aluminum rusts. As you can see, it does not always have good corrosion protection.
