Electrochemical synthesis of polypyrrole/polydopamine for aluminum alloy corrosion inhibition

Polypyrrole(PPy)/polydopamine(PDA) coating was prepared on the surface of 7075 aluminum alloy through electrochemical polymerization to improve the corrosion resistance of aluminum alloy organic coatings. FE-SEM, atomic force microscope and FTIR were used to analyze the surface morphology, surface roughness and chemical composition of PPy/PDA coating, respectively. AC impedance spectroscopy was applied to study the impedance characteristics of the coating. The polarization voltage and polarization current of the aluminum alloy coated with PPy/PDA were analyzed by polarization curves to study the corrosion resistance. The research shows that pyrrole and dopamine simultaneously electrochemically polymerize on the aluminum alloy surface by one-step electrochemical polymerization. PPy molecular chains and PDA molecular chains form network interpenetrating structure. PPy/PDA coating has a sea-island structure with a surface roughness of (73.740±7.811) nm, which is close to the roughness of the pure PPy coating (74.582±7.227) nm. The polarization curves indicate that the corrosion current and corrosion voltages of the coated PPy/PDA coating are 4.1825×10^-6 Acm^-2 and -0.6919 V, respectively. And the corrosion current and corrosion voltages of the pure PPy are 7.618×10^-6 Acm^-2 and -0.7403 V, respectively.