A concept of two steps voltage increasing mode derived from constant voltage mode was developed to fabricate micro-arc oxidation (MAO) coatings on ZK60 Mg alloy. Growth characteristic, microstructure and corrosion resistance of coatings were investigated and compared with the constant voltage mode. An additional and distinguishing stage is found and regarded as a coating regrowth stage playing an important role on coating thickness. Effects of increase value of voltage were also investigated. It shows that rougher and thicker coating is formed for higher value of voltage. And it is more likely to induce destructive arc discharge for excessive increase value, thus leads to a looser and less corrosion resistant coating. The coating formed under two steps voltage-increasing mode of 280-360V exhibits the best corrosion resistance.
Formation of Corrosion-Resistant Films on Al–Zn–Mg Alloy by Steam Coating Using Acidic Zn(NO3)2 Aqueous Solutions