Galvanostatic transient study of anodic film formation on iron in concentrated chloride media

Film formation on iron dissolving anodically in concentrated NaCl and FeCl₂ solutions was investigated galvanostatically in a diffusion cell allowing for uniform current distribution. Induction times for film formation were determined and results were compared to previously reported limiting current data obtained with a rotating disk electrode. In all solutions studied, anodic film formation was found to be induced by precipitation of ferrous chloride at the electrode surface. The surface concentration leading to precipitation was found to be higher than the saturation concentration indicating that supersaturation is required to initiate film formation.