Corrosion cause by varnish and Countermeasures
- When heat and RH are high, the bearing would rust after grease absorb corrosion gas that varnish volatilization inside the motor.
- Most happen to TEFC motor.
- ODC motor wrapping with PE bag.
- During manufacture and storage with high temperature and humid environment (ex. form rainy season to summer、RH at 70% ~ 80%).
- When grease base oil consist of synthetic oil rust more easily compare to mineral oil and silicone oil.
- Solventless based varnish rust easily than solvent based varnish.
- Varnish improper drying time.
- With direction, especially near the rotor and stator inside motor, same as bearing.
- Interior rust more than exterior especially the parts contact with grease.
- Grease with bad smell (even to unpleasant odor).
- Rust pattern grow form point to line and final plane.
- Use solventless based varnish.
- Use without contain non-acid solvent based varnish.
- Adjust the drying time：low temperature with long drying time is better than high temperature with short drying time (ex. 130℃/3hr better than 150℃/1hr).
- Do not install the rotor or stator into motor after varnish drying instantly, suggest that to storage at ventilation place let excess vapor vanish.
- During storage and transportation, avoid heat and humid environment cause varnish volatilization.