Chemical Oxidative Polymerization of Polypyrrole and Its Corrosion Resistance on the AZ31 Magnesium Alloy

Polypyrrole (PPy) was chemically synthesized from pyrrole using sodium p-toluenesulfonate as a doping agent and ferric chloride as an oxidant on the surface of the AZ31 magnesium alloy. Fourier transform infrared (FTIR) spectroscopy was used for structural characterization of the PPy film. The corrosion behavior of the PPy coated AZ31 Mg alloy was studied using an electrochemical polarization test and electrochemical impedance spectroscopy (EIS). Scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDS) were used to observe the surface morphology and for elemental analysis of the film, respectively. The PPy film showed a certain corrosion inhibition on the AZ31 magnesium alloy. Silane pretreatment can improve the corrosion protection performance of the Mg/PPy system causing a positive shift of the corrosion potential by 110 mV and a decrease in the corrosion current density by two orders of magnitude compared with that of AZ31 Mg alloy.