Corrosion Properties of Calcium Stearate-Based Hydrophobic Coatings on Anodized Magnesium Alloy

A calcium stearate-based hydrophobic coating was formed on an anodized magnesium alloy by the electrodeposition method.The influences of the working voltages on the characteristics of the coatings were researched. The results indicate that the working voltages have significant effects on the morphology, thickness, roughness, and wettability of the hydrophobic coatings,but little influence on the phase composition. Higher working voltages promote the nucleation of the coatings during the deposition process. The thickness, roughness, and water contact angle of the coatings increase with the increase in working voltage. In addition, the influences of the working voltages on the corrosion properties and corrosion mechanisms of the coated magnesium alloys are discussed in detail. When the working voltage is 50 V, the best corrosion resistance is obtained, but when the working voltages are 20 V and 100 V, respectively, a low corrosion resistance is obtained because of the presence of the thinner and cracked coating on the substrate surfaces.