Electrochemical behaviour of iron in molten enamel by means of cyclic, square wave and hydrodynamic voltammetry

The electrochemical behaviour of iron present in molten enamel is studied at a platinum disc electrode with cyclic and square wave voltammetry and at a platinum rotating disc electrode using chronoamperometry. Fe(III) is reduced in two steps to a Pt–Fe alloy, which disturbs the oxidation behaviour of Fe(II) considerably. Proof is shown for the formation of the alloy. Indications were found that the chemical equilibrium between Fe(III) and Fe(II) in homogeneous solution is attained slowly, which means that Fe(III) actual concentrations are measured instead of analytical concentrations. A consequence is that the diffusion coefficients determined with cyclic and/or square wave voltammetry and reported in the literature must be corrected. This was shown by using rotating disc chronoamperometry.