Microstructure and Corrosion Properties of ZK60 Alloys Modified by Micro-Arc Oxidation Coatings Using Phosphate- Borate Electrolyte in KOH Solution

摘要

In this work, Na3PO4 (0.05 M) and Na2B4O7 (0.02 M) were used as basic electrolytes for fabricatingmicro-arc oxidation coatings on ZK60 magnesium alloy. The effects of KOH concentrations (0.01,0.05, and 0.1 M) on microstructure, chemical composition, and corrosion resistance weresystematically investigated. The results revealed that MAO-coated samples prepared in 0.05 Maqueous KOH possessed relatively low thickness (8.82 μm), small pore size (3.33 μm), and the lowestporosity (5.156×10-3 pores/μm2). Also, there were no evident microcracks in MAO coatings preparedin 0.05 M aqueous KOH and the pore distribution was uniform. The resulting corrosion characteristicsof MAO-coated ZK60 alloys in simulated body fluid solution (SBF) were significantly affected by theKOH concentration. ZK60 alloy coated with MAO prepared in 0.05 M KOH had relatively high selfcorrosion potential (-1.28 V), highest polarization resistance (2667.23 kΩ·cm2), lowest corrosioncurrent density (4.36×10-7 A·cm-2), and low corrosion rate (1.00×10-5 mm·yr-1), indicating the highestcorrosion resistance in SBF and suggesting that MAO coatings prepared in 0.05 M KOH providedeffective protection from corrosion for magnesium alloys.