Plasma electrolytic oxidation of coupled light metals

Abstract

In order to assess the practicality of plasma electrolytic oxidation of parts consisting of more than one light metal, coupled metals, namely aluminium/AA 7075 aluminium alloy and AA 7075 aluminium alloy/ZE41 magnesium alloy, have been treated under alternating current conditions using constant total currents. Monitoring of the current flow to each component of the couples revealed differences in current densities on each metal, which varied with time. However, for the selected conditions, microdischarges were sustained on both metals and coatings were produced with thicknesses reasonably similar to those of coating on metals treated individually. Further, the transition to ‘soft’ sparking occurred at about the same time on both components of the couples.