Rotor surface coating is a very important process measure in the motor manufacturing process. Its main purpose is to prevent rust and improve appearance. For high-voltage motors, explosion-proof motors and variable-frequency motors, there is also a particularly important purpose, which is to prevent the generation of corona and reduce and eliminate the damage of corona to the motor windings. In the rotor surface coating process, good adhesion is an important indicator. Therefore, the viscosity of the coating material should be controlled during the production and processing, and sufficient drying time should be guaranteed. In the actual processing process, some manufacturers spray the rotor while assembling in order to reduce the assembly time. Even quick-drying paint cannot guarantee that the coating material is completely bonded to the rotor surface. Therefore, the rotor surface of many motors is in a "painted face" state after disassembly. For motors running in a warm environment, some motor rotor surfaces show obvious rust.

In addition to the drying and adhesion requirements, the coating should not be too thick, provided that the basic requirements are met. Especially for induction motors with relatively small air gaps between the stator and rotor, the coating material will cause the air gap between the stator and the rotor to become smaller, affecting the ventilation and heat dissipation of the motor, which will eventually be reflected in the temperature rise level of the motor. In addition, when the adhesion is not good, a thicker coating may cause cracking and shedding of the coating layer during motor operation. These objects will cause noise or even friction problems in the motor. In severe cases, the stator and rotor may become mechanically stuck, which is likely to lead to serious consequences such as burning of the winding. Therefore, whether it is a motor manufacturer or a repair unit, the rotor coating process must be well controlled to prevent unexpected problems.

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