The influence of silicate and sulphate anions on the anodic corrosion and the transpassivity of iron and silicon-rich steel in concentrated KOH solution

摘要

The effect of sulphate and silicate addition in a 10 M KOH electrolyte on the anodic corrosion and trans-passivity of iron and steel rich in silicon are explored by cyclic and linear sweep voltammetry. Formation of ferrate(Vl) in the iron transpassivity region is noticed in all explored electrolytes. The electrochemical sulphato- and silico-ferrate(VI) formation is discussed as a possible result of Fe_3~(III)(Si_(1.32)Fe_(0.68))O_5(OH)_4 and [Fe(II)_4Fe(III)_2(OH)_(12)]SO_4 oxidation in the 10 M KOH electrolytes with silicate and sulphate, respectively. The presence of Fe_3~(III)(Si_(1.32)Fe_(0.68))O_5(OH)_4 in the anodic layer of silicon steel and the crystal structure of electrochemically synthesised Ba(Fe,S)O_4 have been revealed by XRD.