Electrolytic MgO/ZrO2 duplex-layer coating on AZ91D magnesium alloy for corrosion resistance

By a two-step fabrication process of electrolytic deposition and annealing treatment, an MgO/ZrO2 duplex-layer coating has been prepared on AZ91D magnesium alloy as a protective film against corrosion. Owing to the chemical bonding formed after the condensation of precursory hydroxides, the adhesion strength, thickness and compactness of MgO coating on the substrate are significantly enhanced by the intermediate ZrO2 layer which prevents the formation of corrosion product Mg-2(OH)(3)Cl center dot 4H(2)O. As a result, the MgO/ZrO2 duplex-layer coated specimen reveals relatively high corrosion resistance and superior stability in 3.5 wt% NaCl solution with respect to the MgO single-layer coated specimen. (C) 2013 Elsevier Ltd. All rights reserved.