Electrochemical impedance spectroscopy of plastically deformed mild steel

Abstract

An examination of tee influence of plastic deformation on the electrochemical behaviour of mild steel in aqueous acid medium (pH = 1·0) was undertaken hy means of ac impedance measurements. Potentials on the anodic as well as on the cathodic branch of dc polarisation curves were selected. Complex impedance plots exhibited one well defined semicircle with capacity values in agreement with charge transfer processes. An inductive loop was also found but it was not very pronounced. Deformation brought an overall increase in the corrosion current density. The morphology of attack as observed by SEM showed a marked increase in surface roughness on deformed specimens. Two anodic Tafel regions exist for the undeformed material. An analysis of the corrosion mechanisms in the presence of deformation is attempted with capacitance and charge transfer resistance being corrected becauee of the surface roughness effect.