Copper and aluminium tribocorrosion in acid medium : Electrochemical Impedance Spectroscopy investigations

This study is focused on the interests and limits of EIS, Electrochemical Impedance Spectroscopy, to establish the electrochemical behaviour of a tribosystem during friction between copper and aluminium in acid solution. EIS measurements are performed before, during and after friction for understanding electrochemical surface reaction evolution. For each material, calculated capacitance in high frequencies range allows getting further information about the double layer state. The Potential of Zero Charge (PZC) is defined such as the potential value associated to the lowest capacitance. PZC was calculated for copper sample precisely and it was associated to a potential range for aluminium. PZC value of each material is discussed as a key parameter of sliding contact in considered media. Finally, impedance diagrams illustrate a parallel contribution of aluminium and copper during static contact. During wear corrosion tests, EIS results, at high frequencies, are related to the evolution of adsorbed water molecules.