First, when the oxide film layer experiences powdering or grayness, we should first try to see if it can be wiped off. The sealing gray caused by the shutdown process and the powder resulting from electric damage should be cleaned away.
Secondly, we should then analyze the root cause of the oxide powdering issue one by one.
Generally, the powdering of the coating layer is caused by the following factors:
1. The temperature of the oxidation tank is too high;
2. The sulfuric acid concentration is too low;
3. The aluminum ion content exceeds 18 g/L. (The rapid increase in aluminum ion content is often also caused by the high temperature of the oxidation tank, or by the failure to promptly retrieve dropped items in the tank)
If the temperature of the oxidation tank is too high, does it mean the cooling equipment is not large enough? If the cooling capacity is usually adequate, then the size of the chilled water circulation should be considered, and whether the circulating water pump is blocked causing the high temperature-eliminate these issues one by one.
The sulfuric acid content should be based on the daily consumption and replenishment of sulfuric acid in the oxidation tank. Regularly test and replenish the sulfuric acid, keeping the concentration within the process range (optimal 180-220 g/L).
The temperature of the electrolyte has a significant impact on the wear resistance of the oxide film. Generally, if the temperature decreases, the wear resistance of the anodized film on aluminum and aluminum alloys increases because the dissolution rate of the film in the electrolyte decreases. To achieve a higher hardness of the oxide film, it is best to control the temperature within ±2°C when performing hard anodizing.
