Corrosion Resistance and Wear Response of Plasma Spray Nano-Ceramic Composite Coatings on AZ91D Alloy

Herein, various combinations of ceramic coatings (A100-100 wt.% Al₂O₃; AT20-80 wt.% Al₂O₃ + 20 wt.% TiO₂; and AZ20-80 wt.% Al₂O₃ + 20 wt.% ZrO₂) on AZ91D alloys were deposited by optimized plasma spray techniques. Further, the samples were examined for microstructure, phase analysis, corrosion, wear and mechanical properties as per ASTM standards. The corrosion resistance of the coatings was evaluated after a soaking time of 60 min in 3.5 wt.% NaCl solution. Notably, all coatings exhibited a corrosion rate (mpy) substantially lower than that of AZ91D (31.805): A100 (0.665), AT20 (0.283) and AZ20 (0.341). Moreover, these coatings effectively shielded the AZ91D substrates, with a protection level exceeding 98%, against a corrosive 3.5 wt.% NaCl environment. On the one hand, the coated samples reveal the lower wear rates (mm³/N m) of A100 (0.48 × 10⁻⁴), AT20 (0.31 × 10⁻⁴) and AZ20 (0.212 × 10⁻⁴) compared to AZ91D (11.4 × 10⁻⁴). As a result, the composite coatings improved corrosion and wear resistance, thereby extending the life span of magnesium alloys.