A Semi-Mechanistic Model for Predicting the Service Life of Composite Coatings on VW63Z Magnesium Alloy

Abstract

The application of Mg alloys is always accompanied by various coating technology, but a reliable model predicting the service life of coatings on Mg alloys is lacking but urgent. In this work, a semi-mechanistic model was proposed to predict the service life of plasma electrolytic oxidation (PEO) coating/electrophoretic coatings on a VW63Z Mg alloy; the model was decomposed into three parts: a first part depicting the degradation time of organic coating (L₁) and the diffusion time of electrolyte in the inorganic coating (L₂), respectively; a second part interpreting the breakdown of coatings due to the corrosion process (L₃); a final part establishing an algorithm converting the accelerated tests into the real service environment (α); the effect of structural stress and dissimilar metal joints on the service life of coatings was also considered. Based on the ongoing accelerated experiments, the semi-mechanistic model could be able to predict the service life of both PEO coatings and composite coatings on VW63Z Mg alloy with a satisfiable precision.