Complex coating system for improving corrosion resistance of AZ31 magnesium alloy

Abstract

Abstract Complex coating for corrosion protection was developed on magnesium alloy AZ31 using plasma electrolytic oxidation (PEO), spray pyrolysis (SP) and two-part paint. PEO coatings were obtained using electrolyte with phosphate modifier. The oxide layer formed via PEO was sealed using pyrolyzed TiO2 and finally coated with spray primer-paint system to further protect the surface. The specimens were tested for corrosion using immersion gravimetric method in 3% NaCl solution for 1 week and mass loss was recorded. Morphology of the PEO and SP coatings were studied using SEM and chemical analysis of SP coating by EDS. It was found that 30 minutes of spray time in SP process caused surface cracks in the coating. Paint was applied in varying numbers of primer and paint layers and 2 layers each produced the best results in terms of corrosion resistance.