A rapid screening multi-electrode method for the evaluation of corrosion inhibitors

A method is described for the rapid screening of water-soluble corrosion inhibitors, which involves a fixed potential being applied between identical electrodes while immersed in an inhibitor solution. The current flowing between the electrodes is measured and the electrochemical response of the anodic and cathodic reactions, with and without the inhibitor, is then compared. The incorporation of nine pairs of metallic wires (Al, AA2024, AA7075, Fe, mild steel, SS316, Mg, Mg-AZ31 and Zn) into a single assembly enables the effect of inhibitors on different metals to be assessed rapidly. The technique is sensitive to both anodic and cathodic inhibition mechanisms and can provide information on the concentration dependency of inhibitors.This paper provides an electrochemical analysis of the method and demonstrates its application using several soluble chemical species (potassium dichromate, cerium nitrate, sodium vanadate, sodium diphosphate, sodium octanoate) on AA2024-T3 and mild steel at 10⁻² and 10⁻⁴ M and correlates the results with those obtained by conventional potentiodynamic polarization analysis. The errors in the approach were higher for poor inhibitors, however, efficient corrosion inhibitors have decreased experimental errors, thus, ensuring that promising inhibitor candidates are not overlooked.