Characterization of micro-arc oxidation coating post-treated by hydrofluoric acid on biodegradable ZK60 magnesium alloy

Abstract

The porous structure of micro-arc oxidation (MAO) coating is bad to the corrosion resistance and the long-term protective ability of the coating on the biodegradable magnesium alloy. In this study, a hydrofluoric acid (HF) treatment was taken on the MAO coated ZK60 magnesium. It was found that the magnesium fluoride (MgF2) became the main phase and the porous structure of MAO coating disappeared after the HF treatment. Moreover, its wear resistance was at the same level with that of the single MAO coating. Although the corrosion resistance of the coating was slightly decreased, the alkalization effect was well controlled after the HF treatment. The immersion test revealed different degradation behaviors for the MAO coated alloy before and after the HF treatment, and the coating showed no hemolytic potential. In conclusion, the HF treatment is promising as a post treatment method for the MAO coating on biodegradable magnesium alloys.