Mildew is caused by microorganisms. At a certain temperature and humidity (10 to 40 degrees, the most active temperature is 25 to 40 degrees, and the humidity is more than 65%), microorganisms propagate and grow on the surface of aluminum alloy, resulting in locally erasable gray-white spots.
Methods to prevent mould of die-casting aluminum;
1, clean it thoroughly in time, including oil stains and slight oxidation mildew spots on the surface of the workpiece (at this time, the mildew spots are still very small, which can't be seen by the naked eye unless you look carefully). Of course, the common degreasing agents on the market at present, such as kerosene, natural water, diluent, trichloroethylene, dichloromethane, degreasing powder, etc., can not clean the mold spots of aluminum die castings, and have no effect on the mildew, blackening, yellowing and mold spots of aluminum die castings. The most effective way is to use a professional cleaner to thoroughly clean oil stains and mildew spots at one time.
2. Immediately after cleaning, carry out anti-oxidation treatment. It should be noted that chromic acid has been banned at present, and floating, clean, chromium-free and cyanide-free passivator is needed to meet the requirements of environmental protection.