Influence of electrosynthesis potential on corrosion performance of polypyrrole coated stainless steel and its mechanism research

Abstract

The electrosynthesis process of conducting polymer on stainless steel was investigated and a two-step process was adopted to obtain polypyrrole (PPy) films at low potentials. The effects of applied potentials on the electrochemical, structural and protective properties of PPy films have been explored using scanning electron microscopy, infrared spectroscopy, cyclic voltammetry, open circuit potential and potentiodynamic polarisation. Films electrodeposited at lower potentials have more homogeneous morphology and less overoxidation. The electroactivities decrease as applied potentials increase. Polypyrrole films exhibit effective inhibition of corrosion for stainless steel in 3⋅5%NaCl solution. Applying lower potential for the synthesis improves the anticorrosive efficiency of PPy film. The anodic current during polarisation process for stainless steel/PPy is mainly ascribed to the dissolution of stainless steel at pinhole defects for initial immersion, and to PPy oxidation after short time immersion.