Electro Polymerization of Polypyrrole Coatings Doped with Different Proton Acids for Corrosion Protection of 304 Stainless Steel

Polypyrrole (PPY) coatings doped with sulphuric, oxalic and phosphoric acid were prepared on 304 stainless steel (304SS) by electropolymerization. Surface morphology and anti-corrosive performance of the polymer film was investigated by scanning electron microscope and electrochemical tests. The results indicate that the phosphoric acid doped PPY coating has a compact and smooth surface which shifts the E-corr of 304SS towards to more positive value, while the j(corr) was dropped from 10.4 to 0.88 mu A cm(-2). Long-term immersion test shows that the PPY coating doped with phosphoric acid provides better and durable corrosion resistance in comparison with the PPY coatings doped with the sulphuric and oxalic acids.