CORROSION PROTECTION OF MILD-STEEL BY POLYPYRROLE COATINGS IN ACID SULFATE-SOLUTIONS

The corrosion behaviour of mild steel covered by the electrodeposited polypyrrole films was investigated by electrochemical impedance spectr oscopy. Electrodeposition of polypyrrole was performed from aqueous so lution of pyrrole and oxalic acid at a constant current density of 1 m A cm(-2) and yields strongly adherent and smooth polymer layers. The i mpedance spectra were treated through the nonlinear least squares (NLS ) fitting to estimate the parameters of the proposed equivalent circui t, based on physical model for the corrosion of mild steel protected b y polypyrrole films in acid sulfate solutions. (C) 1997 Elsevier Scien ce Ltd.