Three major factors affecting SCC stress corrosion of aluminium sheets

Three major factors affecting SCC stress corrosion of aluminium sheets

Factor one: environmental factors

The environmental factors affecting the stress corrosion of aluminium plates are mainly: ion species, ion concentration, solution pH, oxygen and other gases, corrosion inhibitors, ambient temperature, ambient pressure, etc.

In the study in different atmospheric environment 2A12 and 7A04 two kinds of aluminum plate stress corrosion situation, found that the aluminum plate in different environments stress corrosion sensitivity is different, more sensitive in the marine environment. The marine environment contains a large amount of salt, Cl- will pass through the protective film on the surface of the aluminum plate into the interior, and produce corrosion on it.

Experiments show that when the mass concentration of HNO3 solution between 20% and 40%, the corrosion of aluminum plate intensified, in the concentration of about 35% when the corrosion rate of aluminum plate reached the highest point. And in the concentrated HNO3 solution, the stress corrosion of the aluminum plate is not obvious, the reason for this phenomenon is due to the formation of a layer of dense oxide film on the surface of the aluminum plate, to prevent further corrosion of HNO3.

Factor two: metallurgical factors

Metallurgical factors mainly include the casting method, processing methods and thermal processing of gold stress corrosion, found that the cathodic polarization of the aluminum plate stress corrosion sensitivity increases, friction stir welding stress corrosion sensitivity than fusion welding low.

It is generally believed that by proper treatment of 6061-T6 and 3004 aluminum plate will not appear SCC. Metallurgical factors are different to change the type of aluminum plate surface film, and caused by the different internal organization of aluminum plate and changes in crystal structure, which affects the electrochemical behavior and mechanical behavior of aluminum plate, resulting in different stress corrosion sensitivity of aluminum plate.

Factor 3: Stress factors

Stress factors mainly include the type of load, load size, loading direction, loading speed, etc.. In the case of SCC, the direction of stress must be perpendicular to the grain boundaries so that they can be separated. One of the key factors for stress corrosion is the presence of stress. The combination of alternating stresses and the environment produces corrosion fatigue, which is often distinctly different from stress corrosion rupture due to fixed stresses. Corrosion fatigue usually has more serious consequences than stress corrosion. In addition, the susceptibility of aluminium sheets to stress corrosion can be influenced by differences in loading rates.

The interaction of the three factors becomes the main cause of stress corrosion of aluminium plates, strictly grasp the origin of these three factors, you can well solve the SCC stress problem.