Inorganic-metallic bilayer on Mg alloy via wet and dry plasma treatments

Abstract

The present study investigated the formation of inorganic-metallic bilayer on Mg alloy by combination of wet and dry plasma treatments. For this purpose, Mg alloy subjected to plasma electrolytic oxidation (PEO) in a silicate-based electrolyte was treated subsequently by dry plasma treatment via radio frequency (RF) sputtering to deposit Ni-Cr alloy on the porous inorganic layer. From microstructural observation, Ni-Cr layer modified the morphologies of the porous inorganic layer owing to the conformal coverage. Per electrochemical assessments, sample with bilayer exhibited superior corrosion protection due to the less defective microstructures and the presence of stable oxides. The electrochemical mechanism underlying the superior corrosion resistance of bilayer coating was discussed in the context of an equivalent circuit model by taking the surface morphologies into account.