Fretting Corrosion of Separable Electrical Contacts

The fretting corrosion of separable electrical contacts was studied with different base materials and coatings. The tests were performed on a device which simulates a circuit breaker's separable contact. A vibrator monitored by a microcomputer controlled the vibration amplitude and frequency. The normal contact force was also adjustable. Contact resistance, temperature, and vibrator's excitation current were recorded as a function of time and used to monitor the contact surface degradation. Scanning electron microscopy (SEM) and Xray analysis were used to characterize changes in the coating. In order to accelerate the aging process, the test is quite severe. Most of the coatings show contact resistance degradation after only a few hours. The materials investigated were copper, silver-plated copper and aluminium, tin-based coatings, and nickel coatings. Large differences between these materials were noticed. Also the influence of vibration amplitude, vibration frequency, and normal contact force were evaluated. The main goal of this study was to determine a standard fretting corrosion test for industrial use.