Influence of a Micro-Arc Oxidation/Poly-Lactic Acid Composite Coating on Corrosion Resistance of Extruded Mg-2Zn-0.5Zr-1.5Dy (Mass%) Alloy

Micro-arc oxidation (MAO) coating can significantly slow down the repaid degradation rate of biodegradable magnesium alloy, but the porous characteristics of the coating cannot provide long-term protection to magnesium alloy. In this paper, poly-lactic acid (PLA) was used to seal the porous MAO coating on the surface of extruded Mg-2Zn-0.5Zr-1.5Dy (mass%) magnesium alloy by a dipping coating method. Assessments were conducted by electrochemical experiment, immersion test, and hydrogen evolution experiment. The result shows that after the MAO-coated sample was dipped in PLA solution four times, the PLA could largely seal the porous and cracks of the MAO coating, and a dense MAO/PLA composite coating with a thickness of ~ 50 μm was prepared. The MAO/PLA composite coating provides good and stable protection to the alloy under 0~56 d immersion in the simulated body fluid than the single MAO coating, which shows an excellent application potential in the field of biodegradable magnesium alloy.