MaryellenT
08-12-2020, 05:45 AM
<p>
Corrosion has always been the primary factor affecting the service life of aluminium plates. Although the aluminium sheet treated by a certain process can be used in complex environment, due to many factors causing corrosion of the aluminium sheet, no perfect process can guarantee that the aluminium sheet plate will not be corroded. The main causes of corrosion of aluminium sheet: environmental factors, metallurgical factors and stress factors<br></p>
<p>
1. Environmental factors</p>
<p>
The main environmental factors affecting stress corrosion of aluminium sheet are ion species, ion concentration, solution pH value, oxygen and other gases, corrosion inhibitors, environmental temperature, environmental pressure and so on. The stress corrosion susceptibility of aluminium sheet is different in different environments, and it is more sensitive in marine environments. There is a lot of salt in the marine environment. Cl - will pass through the maintenance film on the surface of the aluminium plate and enter into the interior, which will cause corrosion.</p>
<p>
Experiments show that when the mass concentration of HNO3 solution is between 20% and 40%, the corrosion of aluminium sheet intensifies, and the corrosion rate of aluminium sheet reaches the highest point when the concentration is about 35%. In concentrated HNO3 solution, the stress corrosion of aluminium sheet is not obvious. The reason for this phenomenon is that a dense oxide film formed on the surface of aluminium sheet, which prevents the further corrosion of HNO3.</p>
<p>
2. Metallurgical factors</p>
<p>
Metallurgical factors mainly include casting mode, processing mode and stress corrosion of hot spot gold. It is found that cathodic polarization increases the stress corrosion sensitivity of aluminium plate, and friction stir welding has lower stress corrosion sensitivity than fusion welding.</p>
<p>
It is generally believed that 6061-T6 and 3004 aluminium plate properly treated will not be corroded. The different metallurgical factors change the type of outer film of aluminium sheet, and result in different internal structure and crystal structure of aluminium sheet, which affect the electrochemical and mechanical behavior of aluminium sheet and lead to different stress corrosion susceptibility of aluminium sheet.</p>
<p>
3. Stress factors</p>
<p>
Stress factors mainly include load type, load size, loading direction, loading speed and so on. As far as corrosion is concerned, 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 stress. Different stress effects will produce different effects. Alternating stress and environmental interaction will lead to corrosion fatigue, which is usually different from stress corrosion cracking under fixed stress. Corrosion fatigue is usually more serious than stress corrosion. In addition, the stress corrosion sensitivity of aluminium sheet is also affected by the different loading speed.</p>
Corrosion has always been the primary factor affecting the service life of aluminium plates. Although the aluminium sheet treated by a certain process can be used in complex environment, due to many factors causing corrosion of the aluminium sheet, no perfect process can guarantee that the aluminium sheet plate will not be corroded. The main causes of corrosion of aluminium sheet: environmental factors, metallurgical factors and stress factors<br></p>
<p>
1. Environmental factors</p>
<p>
The main environmental factors affecting stress corrosion of aluminium sheet are ion species, ion concentration, solution pH value, oxygen and other gases, corrosion inhibitors, environmental temperature, environmental pressure and so on. The stress corrosion susceptibility of aluminium sheet is different in different environments, and it is more sensitive in marine environments. There is a lot of salt in the marine environment. Cl - will pass through the maintenance film on the surface of the aluminium plate and enter into the interior, which will cause corrosion.</p>
<p>
Experiments show that when the mass concentration of HNO3 solution is between 20% and 40%, the corrosion of aluminium sheet intensifies, and the corrosion rate of aluminium sheet reaches the highest point when the concentration is about 35%. In concentrated HNO3 solution, the stress corrosion of aluminium sheet is not obvious. The reason for this phenomenon is that a dense oxide film formed on the surface of aluminium sheet, which prevents the further corrosion of HNO3.</p>
<p>
2. Metallurgical factors</p>
<p>
Metallurgical factors mainly include casting mode, processing mode and stress corrosion of hot spot gold. It is found that cathodic polarization increases the stress corrosion sensitivity of aluminium plate, and friction stir welding has lower stress corrosion sensitivity than fusion welding.</p>
<p>
It is generally believed that 6061-T6 and 3004 aluminium plate properly treated will not be corroded. The different metallurgical factors change the type of outer film of aluminium sheet, and result in different internal structure and crystal structure of aluminium sheet, which affect the electrochemical and mechanical behavior of aluminium sheet and lead to different stress corrosion susceptibility of aluminium sheet.</p>
<p>
3. Stress factors</p>
<p>
Stress factors mainly include load type, load size, loading direction, loading speed and so on. As far as corrosion is concerned, 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 stress. Different stress effects will produce different effects. Alternating stress and environmental interaction will lead to corrosion fatigue, which is usually different from stress corrosion cracking under fixed stress. Corrosion fatigue is usually more serious than stress corrosion. In addition, the stress corrosion sensitivity of aluminium sheet is also affected by the different loading speed.</p>