The effect of PPY powder on the anticorrosive performance of a duplex cerium/epoxy coating

Polypyrrole powder was chemically synthesized using cerium tartrate as an oxidant. The powder was loaded into an epoxy resin to create a protective coating onto AZ91D Mg alloy. The coatings consisted of an inner ceriumbased film and an epoxy layer loaded with different amounts of polypyrrole (0.2-5 wt%) on top. Infrared spectroscopy and Energy Dispersive X-Ray spectroscopy analysis were used to characterize the polymer powder. The anticorrosive properties of the coatings were studied in NaCl containing solution by applying electrochemical measurements such as polarization, electrochemical impedance spectroscopy (EIS), and open circuit potential (OCP). Solution analysis was done to check the electrochemical results obtained. The corrosion resistance was remarkably improved by the addition of the polypyrrole. The best anticorrosive properties were achieved when the epoxy layer was loaded with 1 wt% of PPy. The results show a decrease in corrosion current density from 2.763 x 10-6 to 2.770 x 10-7 mA cm-2 when the polymer was loaded. In addition, the filler reduces the water absorption of the epoxy coating from 9 to 7%. The protective properties were attributed to the barrier behavior of the epoxy film, the corrosion inhibition effect of the PPy, and the self-healing effect of the cerium compounds present in the PPy powder.