How is Aluminum plate corrosion caused?
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How is Aluminum Plate Corrosion Caused?
Aluminum plate corrosion has always been the primary factor affecting the life of aluminum plates. Although the aluminum plate processed by a certain process can be used in a complicated environment, there are many factors causing the aluminum plate corrosion, and the perfect treatment process cannot ensure that the aluminum plate does not corrode. There are three main reasons for the corrosion of aluminum plates: environmental factors, metallurgical factors and stress factors, which are mutually influential.
The Three Major Factors that Cause Aluminum Plate Corrosion
Environmental factors affecting aluminum plate corrosion include: ion species, ion concentration, solution pH, oxygen and other gases, corrosion inhibitors, ambient temperature, and ambient pressure.
The stress corrosion of 6063 aluminum plate and 5083 aluminum plate in different atmospheric environments was studied. It was found that the aluminum plate has different stress corrosion sensitivity in different environments and is sensitive in the marine environment. The marine environment contains a large amount of salt, and Cl- will enter the interior through the maintenance film on the outer surface of the aluminum plate, causing corrosion.
The experiment indicates that when the mass concentration of HNO3 solution is between 20% and 40%, the corrosion of the aluminum plate is intensified, and the aluminum plate corrosion rate reaches the highest point when the concentration is about 35%. In the concentrated HNO3 solution, the stress corrosion of the aluminum plate is not obvious. The reason for this phenomenon is that a dense oxide film is formed on the surface of the aluminum plate, which prevents further corrosion of HNO3.
The metallurgical factors mainly include the casting method, processing method and the influence of gold stress corrosion at the hot point. It is found that the cathodic polarization increases the stress corrosion sensitivity of the aluminum plate, and the stress corrosion sensitivity of the friction stir welding is lower than that of the fusion welding.
Corrosion does not occur with properly treated 6061-T6 aluminum plate and 3003 aluminum plate. The difference of metallurgical factors changes the type of aluminum film, and causes the internal structure of the aluminum plate and the crystal structure to change, which affects the electrochemical behavior and mechanical behavior of the aluminum plate, resulting in different stress corrosion resistance of the aluminum plate.
3. Stress factors
Stress factors mainly include load type, load size, loading direction, loading speed, and so on. In the case of corrosion, the direction of stress must be perpendicular to the grain boundary so that it can be separated. One of the key factors in the occurrence of stress corrosion is stress effect. Different stress effects will produce different effects. Corrosion fatigue occurs when alternating stress and environment work together, which is obviously different from stress corrosion cracking that occurs with fixed stress. Corrosion fatigue is usually more serious than stress corrosion. In addition, the difference in loading speed also affects the sensitivity of aluminum plate stress corrosion.
The above three factors are often mutually influential. Even if the simple treatment process can prevent the aluminum plate from being affected by an environmental corrosion, it is difficult to avoid corrosion in the other two environments. Therefore, we must consider the use environment of the aluminum plate and do a good job of anti-corrosion work.