Any magnet that's been sitting around for a while will have spots of some other color on the surface that will slowly turn to rust. Only after coating is easy to appear rust spots. Rust spots appear for several reasons, air flow moist places, where the temperature difference is large. And the dirt on the surface of the magnet before electroplating is not cleaned well, or the plating time and process are not good enough, and the magnet packaging and sealing damage caused by the oxidation of the magnet.
In general, special working conditions require magnetic coatings. For example, the magnet used in the motor, relatively wet working environment, so must be treated with surface coating. At present, the main coating technology of magnets are: galvanized, color galvanized, nickel plating, black nickel plating, nickel copper nickel, gold plating, silver plating, epoxy resin plating. And galvanized and nickel plating is the most common plating process, each coating surface color is not the same, all the prices are not the same. Galvanized surface is silver, can do 12 to 48 hours of salt spray test, if the plating effect is good, can be preserved for two to five years, which is also the price advantage of galvanized, relatively low. Nickel plating luster looks like stainless steel, it is indeed difficult to be oxidized in the air, and the appearance and luster are relatively good, can be carried out 12 to 78 hours of salt spray test, but it is also obvious that if the use of glue will make the coating fall off and accelerate the oxidation.
Even qualified salt spray test products, in long-term storage or harsh environment work, there will be rust spots. Generally in order to prevent the occurrence of magnet rust, or the use of electroplating to prevent corrosion is the most effective.
