Experiments were performed to study the contact resistance changes of several common connector contact materials (0.2%Co hard gold plate, Diffuse Gold Alloy (DGR-156), tin plated copper alloy and silver plated copper alloy) at 150/spl deg/C. The emphasis was on contact degradation due to thermal expansion type of relative contact interface movement, i.e. low frequency (<0.01 Hz) and large wipe distance (>100 /spl mu/m) fretting. The contact samples were the standard dimple-flat configuration. Electrical degradation in the form of contact resistance rise was measured. Scanning Electron Microscopy and Energy Dispersive Spectroscopy were used to analyze the surface morphology and composition changes. For the precious metal coating (Hard Au plate, DGR-156 and Ag plate), wear through of the plating layer was found to be the cause of resistance increase. For the non-noble plating such as tin, contact resistance increased with oxide accumulation. Suitable lubricants were demonstrated to be effective for Sn plating to delay the resistance rise.