Aluminium and its alloy can be corroded in most atmosphere. It is particularly more severe in sea atmosphere due to the excessive presence of chloride ion which aid corrossion more easily. On aluminium die-casting surface, there are many holes cohere corrosion reactions are taking place rapidly. After chromates treatment, aluminium die casting is coated with a layer of surface protection. Thus, cot- Aluminum and its alloy can be corroded in most atmosphere. It is particularly more severe in sea atmosphere due to the excessive presence of chloride ion which aid corrossion more easily. On aluminum die-casting surface, there are many holes cohere corrosion reactions are taking place rapidly. After chromates treatment, aluminum die casting is coated with a layer of surface protection. Thus, cot-