The influence of pH on corrosion inhibitor selection for 2024-T3 aluminium alloy assessed by high-throughput multielectrode and potentiodynamic testing

This paper complements our recently published work on the development of a high-throughput scanning technique for corrosion inhibitors named multielectrode. The multielectrode set-up, fully described in the previous work, combines nine pairs of different metals in a single multi-metal electrode configuration. In the working procedure a fixed potential is applied between identical metallic electrodes while immersed in an inhibitor solution, without the use of a reference electrode. The current flowing between the electrodes is measured and the combined electrochemical response of the anodic and cathodic reactions, with and without inhibitor, is then characterized. The methodology allows approximately 30 electrochemical experiments to be performed per hour, the rapid identification of inhibitors able to protect different metals, and the rapid detection of the optimal inhibitor concentration.The present work evaluates the influence of solution pH on the anticorrosion performance of three different inhibitors (CeCl₃, Ce(dbp)₃ and K₂Cr₂O₇) on 2024-T3 aluminium alloy (AA2024-T3) by means of conventional potentiodynamic polarization analysis and the multielectrode technique reported previously. The usefulness of the high-throughput multielectrode technique to detect the influence of the solution pH on the anticorrosive performance of different inhibitors has been studied and its correlation with traditional potentiodynamic polarization testing evaluated. The possible reasons for non-correlation between techniques are studied, and those considered important, highlighted. The combined dependence of corrosion inhibition on factors including pH, inhibitor type, and metal cross-contamination was also investigated showing that the multielectrode is a robust technique to detect efficiency changes due to pH variations.