Effect of Coating Contact Materials (Sn, Ag, Au) on Power Contact Voltage Fluctuation During Fretting Corrosion

International audienceYrtttvaf, corrosion phenomenon is known as the main cause of contact voltage fluctuation in tin, Ag and Au coatcd materials contact at low level. Until now, these investigations were done with low current (a few milliamps), an unrealistic value for some higher current automotive applications. Indeed, in these cases, the joule effect due to fretting voltage increases, leading to heat the contact zone with some consequences like increasing oxidation, or softening Sn coating. Furthermore, higher voltage (up to 14V), induces large voltage fluctuations and subsequent arcing occurrence are observed. In this work, we will determine the relationship between the coating nature and fretting voltage characteristics, especially fluctuation and level evolution. For this aim an experimental study was done on sphere/plan contacts made with cooper, coatcd with tin, silver and gold. These contacts are submitted to vibration amplitudes up to 100 micrometers at frequencies of a few 50Hz, under a current of 10A and a voltage of 16VDC. The average contact fluctuations are measured during one cycle while fast fluctuations inside the cycles are measured by oscilloscope Indeed, the analysis of the voltage fluctuations in term of level and time appearance is a very useful tool to analyze in-situ fretting behavior. Upon analysis of experimental data, it is found that noble coating (Ag, Au) show lower and delayed average voltage fluctuations over the cycle. Moreover, fast fluctuations can reach arc voltage with variable occurrences and time