1. Electroplating time is not enough, it dues to the problem of process flow;
2. Air liquidity of the location where motorized pulley stores is not good, or the location is wet, it is may due to the large difference in temperature;
3. If the package sealing breaks, the motorized pulley may oxidate and get rusty;
4. The most important point is that before electroplating, the dirt on motorized pulley surface is not being cleaned well, it is also one of the reasons why the motorized pulley will get rusty.