Optimization of the two-step coating formation process for ZK21 magnesium alloy

Abstract

The primary hindrance to the broader utilization of magnesium alloys lies in their insufficient corrosion resistance. This research initiative introduced an advanced two-phase methodology incorporating phosphating and alkali heating to produce a protective Ca-P coating on the surface of magnesium alloys. This innovative approach not only bolsters their corrosion resistance but also facilitates controlled degradation in bodily fluid environments. Following a 60-minute phosphating process in a solution with a pH level of 3, the resultant CaP coating achieved full coverage over the magnesium alloy surface, displaying commendable coating density and uniformity. Subsequent treatment with alkali heating for 30 minutes further enhanced the density and smoothness of the coating. Analysis utilizing EDS and XRD revealed that the primary constituents of the phosphate magnesium alloy and the phosphate + alkali heated magnesium alloy coating were DCPD and HA, respectively. Corrosion degradation assessments conducted in SBF solution validated that the two-step coating formation method significantly fortified the corrosion resistance of magnesium alloys.