Kinetics and mechanism of the iron electrode in solutions of HCl in dimethylsulphoxide

Abstract

The kinetics of polycrystalline iron electrodes has been investigated under different experimental conditions, employing solutions of hydrogen chloride in dimethylsulphoxide in the presence of KClO₄ as supporting electrolyte. Anodic E/I curves exhibit active and passive regions, the former having a Tafel slope of 2RT/3F. At the lower cathodic polarizations, hydrogen discharge occurs and at higher, the electrodeposition of ferrous ion takes place; both reactions have Tafel slopes of 2RT/F. Other kinetic parameters obtained include the reaction orders, dependence of corrosion potential on HCl concentration, non-steady slopes from decay curves, experimental activation energy, etc. The interpretation of the reactions is given in terms of a consecutive reaction mechanism involving the participation of solvent ions. The reaction scheme is formally the same as already discussed for the iron electrode in aqueous solutions to explain the 2RT/3F anodic Tafel slope.