Electropolymerization of pyrrole on AZ31 Mg alloy and study of coating parameters to enhance corrosion resistance

Polypyrrole (PPy) was electrochemically synthesized on AZ31 Mg alloy in a solution containing sodium salicylate and pyrrole using cyclic voltammetry. Through taking advantage of electrochemical impedance spectroscopy and potentiodynamic polarization measurements, the effect of some electropolymerization parameters like potential, monomer concentration and number of cycles on the quality and protective performance of the PPy coating applied on the Mg alloy was studied. In the presence of the PPy coating synthesized in the optimal conditions, the charge transfer resistance and corrosion current density encountered a significant increase and drop, respectively. Furthermore, corrosion potential shifted toward more noble values. Scanning electron microscopy (SEM) studies revealed a cauliflower morphology for the PPy film synthesized on the Mg alloy. The grain size ranged from 30 to 50 nm.