Because of its excellent performance, Aluminum Die Casting are widely used in electronics, home appliances, automobiles and other industries, and many precision aluminum castings can also be used in military fields such as ships. Therefore, aluminum die casting have always been a hot commodity in component procurement. Many times, shortly after we purchased aluminum die casting, the spots appeared on the surface of aluminum die casting, which caused us troubles.

Before we know why spots appear on the surface of aluminum die casting, we should have a detailed understanding of aluminum die casting. Aluminum die casting is to make the aluminum surface smoother by phosphating the aluminum surface first, then alkaline electrolytic polishing process, and then chemical polishing and electrochemical surface strengthening treatment, which is a better film formation on the aluminum surface for production needs. Knowing how aluminum die casting are formed, let’s find out why spots appear on the surface of aluminum die casting. Because die castings are metal and contain many metal elements, such as aluminum and iron, when placed in the air, they will inevitably come into contact with water vapor and oxygen in the air and have chemical reaction. However, the following situations will aggravate the occurrence of mildew spots:

1. The storage location has high humidity.

2. The surface of die casting is loose.

3. Excessive corrosion of cleaning agent for die casting.

4. Die castings are not dried after corresponding procedures (such as cleaning and electroplating, etc.).

Therefore, after understanding the principle, here are some suggestions on how to prevent mildew spots:

1. The die-cast workpieces shall be placed in a dry and ventilated place.

2. Carefully select cleaning agents. Some cleaning agents will cause discoloration of the workpiece surface.

3. If there are no special circumstances, it is recommended not to stay for more than 5 days. It should be degreased and cleaned in time, passivated and dried with trivalent chromium or chromium-free, and then put into storage.

4. Choose aluminum die casting with better performance.

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