Chrome-free zirconia-based protective coatings for magnesium alloys

Environmentally friendly anti-corrosion surface treatment based on zirconium conversion coating was developed for magnesium AZ31D alloy. The effect of zirconate solution concentrations on the corrosion protection performance of magnesium substrate was studied. EIS and cyclic voltammetry techniques were used to evaluate the corrosion behavior in 3.5% NaCl. The surface resistance (Rp) of the uncoated AZ31D measured by EIS was approximately about 2.1 × 103 Ω cm2. Rp increased by factor 8 times for samples treated by zirconate dilute solution. The optimum conditions to obtain protective coatings for AZ31D were determined. Surface examination of the samples was investigated using SEM-EDS and macroscopic images.