Electrosynthesis of PAni/PPy coatings doped by phosphotungstate on mild steel and their corrosion resistances

• Electrodeposition of PAni/PPy doped by phosphotungstate (PW12) on mild steel.
• Introduction of PW12 improves the conductivity of conducting coatings.
• OCPs of conducting coatings shift toward positive with the incorporation of PW12.
• PAni/PPy-PW12 exhibits better corrosion resistance than PAni-PW12/PPy.

Polyaniline/polypyrrole (PAni/PPy), polyaniline-phosphotungstate/polypyrrole (PAni-PW12/PPy) and PAni/PPy-PW12 have been successfully electrodeposited on mild steel (MS) by cyclic voltammetry in aqueous oxalic acid solutions. It was found that the incorporation of PW12 enhanced the corrosion resistance of PAni/PPy coating. Moreover, in comparison to PAni-PW12/PPy, PAni/PPy-PW12 coating exhibited better corrosion resistance for mild steel. After immersion of 36 h in 0.1 M HCl, for instance, the polarization resistance of PAni/PPy-PW12 coating reached 1695 Ω cm2, more than those of both PAni/PPy and PAni-PW12/PPy.