Fabrication and Corrosion Resistance Evaluation of Novel Epoxy/Oxide Layer (MgO) Coating on Mg Alloy

A protective novel (MgO) oxide layer (with 91.92% corrosion protection efficiency) was successfully applied on Mg–0.4%Ca alloy using protective oxidation at 390°C (without any pre-treatment). Oxide layer coated Mg alloy was then coated with pure epoxy coating (as top coat). This oxide inner barrier layer protected Mg substrate from 3.5wt % NaCl solution when it passes through from epoxy top layer. Lowest anodic current density and highest charge transfer resistance (1118.124 kΩ cm 2 ) and impedance modulus (│Z│) at low frequency substantiated that the existence of thick epoxy top layer which is integrated ( via physical anchoring) with the oxide inner barrier layer could considerably reduce the corrosion rate of magnesium substrate in the chloride containing solutions. Moreover, corrosion mechanism for coated Mg–0.4%Ca alloys was then suggested.