Electrochemical polymerization of dopamine with/without subsequent PLLA coating on Mg-Zn-Y-Nd alloy.

• Electropolymerized dopamine (ePDA) coating was prepared on Mg-Zn-Y-Nd alloy surface. • ePDA coating surface is uniform and doped with salicylate and magnesium. • ePDA coating induced more uniform surface of Poly (l -lactic acid) (PLLA) coating than dip polydopamine (dPDA) coating. • ePDA/PLLA coating showed excellent adhesion and higher corrosion resistance than dPDA/PLLA coating. The high surface roughness of dip polydopamine (dPDA) coating on magnesium alloy could decrease the quality of secondary modification. In the present study, we report an electropolymerized dopamine (ePDA) coating on Mg-Zn-Y-Nd alloy from sodium salicylate aqueous solutions by galvanostat method to address this problem. The coating formation process and coating structure were investigated. Then, a Poly (l -lactic acid) (PLLA) coating was prepared on ePDA and dPDA treated samples. The SEM results reveal that the ePDA film appeared to be more uniform than dPDA coating and was doped with salicylate and magnesium ions. ASTM D3359 -09 "Tape test" shows excellent adhesion of the ePDA/PLLA layer. The electrochemical impedance spectroscopy and polarization curves demonstrate ePDA/PLLA film has a better corrosion resistance than dPDA/PLLA film, owing to the structural difference of polydopamine anchoring layer. [ABSTRACT FROM AUTHOR]