On the contact resistance between surface-oxidized metals in repeated sliding

Abstract Electrical contact resistance and coefficient of friction were measured for the purpose of investigating contact between metal surfaces subjected to repetitive reciprocating sliding. A pendulum-type friction device was used and contact resistance was recorded automatically. Steel and copper were studied under natural and surface-oxidized conditions. With steel the trace of contact resistance during sliding fluctuated in both cases, but with copper it was either smooth or fluctuating under natural or oxidized condition, respectively. Influence of oxygen content in the atmosphere on the nature of the oxide layer was also studied with tin; it was shown that the trace of resistance became smooth in air at a pressure of 1 mm Hg, but fluctuated in atmospheric air. These experiments suggest that the nature of the oxide layer affects the size of worn oxide debris, and this determines whether the trace is smooth or fluctuating and the value of resistance low or high.