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Aluminum plate corrosion is how to happen?

addtiame:2016/11/01 click:
Aluminum plate corrosion is how to happen?

Corrosion is the most important factor that affects the service life of aluminum sheet. Although the aluminum sheet can be used in a complex environment, but because of the many factors that cause the corrosion of the aluminum plate, the perfect treatment process can not guarantee that the aluminum plate will not be corroded. There are three main reasons for the corrosion of aluminum plate: environmental factors, metallurgical factors and stress factors, the three are mutually influenced.

1, environmental factors

The environmental factors that affect the stress corrosion of aluminum plate mainly include: ion species, ion concentration, pH value of solution, oxygen and other gases, corrosion inhibitor, environmental temperature, environmental pressure and so on.

The stress corrosion of 2A12 and 7A04 in different atmospheric environments was studied. It was found that the stress corrosion sensitivity of the aluminum plate was different in different environments, and the marine environment was more sensitive to the two kinds of aluminum plate. Marine environment contains a lot of salt, Cl- will go through the outer surface of the aluminum plate to maintain the film into the interior, resulting in corrosion.

The experiment shows that when the mass concentration of HNO3 solution is between 20%~40%, the corrosion of aluminum plate is increased, and the corrosion rate of aluminum plate reaches the highest point when the concentration is about 35%. In concentrated HNO3 solution, the stress corrosion of aluminum plate is not obvious. The reason of this phenomenon is that a dense oxide film is formed on the outer surface of the aluminum sheet, which prevents the HNO3 from further corrosion.

2, metallurgical factors

The metallurgical factors mainly include casting, machining and heat stress corrosion effects of gold, found that the cathode polarization aluminum increase of stress corrosion sensitivity, friction stir welding stress corrosion sensitivity than low welding.

It is generally believed that the appropriate treatment of 6061-T6 and 3004 aluminum plate will not appear corrosion. The different types of metallurgical factors changed the appearance of aluminum film and aluminum, caused by the internal organization of the different crystal structure changes, thus affecting the electrochemical behavior and mechanical behavior of aluminum, lead to aluminum stress corrosion sensitivity of different.

3, stress factors

Stress factors mainly include the type of load, load size, load direction, loading speed, etc.. In terms of corrosion, the stress direction must be perpendicular to the grain boundary so that it can be separated. One of the key factors of stress corrosion is the stress action. Different stress effects can produce different effects, the alternating stress and the environment interaction occur corrosion fatigue, and the stress corrosion cracking usually have obvious difference. Usually the corrosion fatigue is more serious than the result of stress corrosion. In addition, the different loading speed also affects the sensitivity of aluminum plate stress corrosion.

These three factors are often mutually affected, the simple process even if the aluminum plate can not be affected by an environmental impact, it is difficult to avoid the corrosion of the other two kinds of environment. So to take into consideration the aluminum using environment, anticorrosion work.