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

Shangjun Ma
2018 International Journal of Electrochemical Science  
In this work, Na 3 PO 4 (0.05 M) and Na 2 B 4 O 7 (0.02 M) were used as basic electrolytes for fabricating micro-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 were systematically investigated. The results revealed that MAO-coated samples prepared in 0.05 M aqueous KOH possessed relatively low thickness (8.82 µm), small pore size (3.33 µm), and the lowest porosity
more » ... st porosity (5.156×10 -3 pores/µm 2 ). Also, there were no evident microcracks in MAO coatings prepared in 0.05 M aqueous KOH and the pore distribution was uniform. The resulting corrosion characteristics of MAO-coated ZK60 alloys in simulated body fluid solution (SBF) were significantly affected by the KOH 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·cm 2 ), lowest corrosion current density (4.36×10 -7 A·cm -2 ), and low corrosion rate (1.00×10 -5 mm·yr -1 ), indicating the highest corrosion resistance in SBF and suggesting that MAO coatings prepared in 0.05 M KOH provided effective protection from corrosion for magnesium alloys.
doi:10.20964/2018.07.13 fatcat:knu4sjfx5vf5jaxmifbv6sykuy