The effect of power on low frequency fretting corrosion

A series of low frequency fretting experiments have been conducted on a purpose built apparatus. The tests have used tin/lead plated contact surfaces to investigate the effect of electrical power on the process of fretting corrosion at these frequencies. The test samples comprised of a hemispherical rider resting on top of a flat coupon. The experimental conditions for each test were fixed at: 80 microns displacement, 2.38 mHz frequency, 100 gf normal force and room temperature. Contact resistance measurements were taken at discrete intervals during each fretting wear cycle. These were made using the four wire method at dry circuit conditions (<20 mV, <100 mA). On the completion of the tests, micrographs were taken using the Scanning Electron Microscope and depth profiles made using Auger Electron Spectroscopy. The results showed that those samples powered with a constant current survived a larger number of fretting wear cycles before open circuit conditions occurred. This is thought to be due to the applied voltage assisting in the breakdown of the insulating films. The results have been compared to earlier work carried out at high frequency which produced the opposite effects. A hypothesis is presented to explain the differences.