Improving the phosphating process for Ca-P coating on ZK21 biomedical magnesium alloy

Abstract

Abstract The optimization study of the phosphating process was conducted on the surface of ZK21 biomedical magnesium alloy using the chemical conversion technique to fabricate Ca-P coating. The findings reveal that the optimal concentrations of the three additives in the phosphating solution, Ca(CH3COO)2, C6H4O5NSNa, and Na2MoO4, are 12 g/L, 2 g/L, and 0.5 g/L, respectively. Under these specified conditions, the resulting Ca-P coating appears compact and uniform. An optimal quantity of Ca(CH3COO)2 can enhance the concentration of Ca2+ in the solution. C6H4O5NSNa accelerates the rate of membrane formation, whereas Na2MoO4 facilitates the creation of nucleation sites, consequently bolstering membrane formation even further. Analysis through EDS and XRD confirmed that the predominant compound in the Ca-P coating is CaPO3(OH)2·2H2O (DCPD).