Corrosion has always been the primary factor affecting the life of the aluminum round disc. Although the aluminum round disc processed in a certain process can be used in a complicated environment, there are many factors that cause corrosion of the aluminum round disc, and the perfect processing process cannot guarantee that the aluminum round disc will not corrode. There are three main reasons for corrosion in aluminum round disc: environmental factors, metallurgical factors and stress factors
1. Environmental factors
The environmental factors affecting the stress of aluminum round disc are: ion species, ion concentration, solution pH, oxygen and other gases, corrosion inhibitors, ambient temperature, ambient pressure, etc.
The stress corrosion of 2a12 and 7A04 two round round discs in different atmospheric environments was studied. It was found that the aluminum round disc has different stress corrosion susceptibility 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 of the aluminum round disc, causing corrosion.
The experiment indicates that when the mass concentration of the HNO3 solution is between 20% and 40%, the corrosion of the aluminum round disc is intensified, and the corrosion rate of the aluminum plate reaches the highest point when the concentration is about 35%. In concentrated HNO3 solution, the stress corrosion of aluminum round disc 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.
2. Metallurgical factors
The metallurgical factors mainly include the casting method, the processing method and the influence of gold stress corrosion at the hot point. It is found that the cathodic polarization makes the aluminum round disc stress corrosion sensitivity increase, and the stress corrosion sensitivity of friction stir welding is lower than that of the fusion welding.
Corrosion does not occur with properly treated 6061-T6 and 3004 aluminum round discs. The difference in metallurgical factors changes the type of aluminum round disc, and causes the internal structure of the aluminum round disc to change and the crystal structure changes, thus affecting the electrochemical behavior and mechanical behavior of the aluminum round disc, resulting in aluminum round disc stress corrosion sensitivity. Different sex.
3. Stress factors
Stress factors mainly include load type, load size, loading direction, loading speed, and the like. 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 the need for stress. Different stress effects will produce different effects. Corrosion fatigue occurs when alternating stress and environment work together, and stress corrosion cracking which occurs with fixed stress is usually significantly different. Corrosion fatigue is usually more serious than stress corrosion. In addition, the difference in loading speed also affects the sensitivity of aluminum round disc stress corrosion.
