The corrosion protection of mild steel by polypyrrole/polyphenol multilayer coating

Electrochemical synthesis of very thin polyphenol (PPhe) film was achieved on polypyrrole coated mild steel electrode (MS/PPy) and a multilayer coating was obtained, cyclic voltammetry technique was used for the synthesis. The corrosion performance of this multilayer coating and single PPy coating were investigated in 0.05 M H2SO4 solution by using electrochemical impedance spectroscopy (EIS), anodic polarization curves and open circuit potential (E-ocp)-time curves were used. It was found that the multilayer coating could provide much better protection than the single PPy coating for corrosion of MS for much longer periods and an efficiency of 98.3% was determined for this coating after 340 It exposure time in corrosive medium. it is proposed that the very thin PPhe film coated on top of PPy coating lowered the porosity and improved the barrier effect of the coating significantly. (C) 2004 Elsevier Ltd. All rights reserved.