Discovering synergistic localised corrosion inhibitors through local polarisation measurements using electrode arrays

A new approach to discovering effective inhibitors for localised corrosion control is demonstrated through probing the mechanistic behaviour of chemical inhibitors and combining inhibitors with complementary corrosion inhibition mechanisms. An electrochemically integrated multi-electrode array is used to identify chemicals with complementary corrosion inhibition mechanisms through the measurement and analysis of local polarisation curves. This approach has been verified by the discovery of a highly effective synergistic localised corrosion inhibitor from the combination of single inhibitors with complementary mechanisms identified through analysing local polarisation curves. The inhibition efficiencies and mechanisms of two chemical inhibitors, cetyltrimethylammonium bromide (CTAB) and lanthanum(III) 4-hydroxycinnamate (La(4OHcin)3·5H2O), were probed by mapping current distributions across different regions of the weldment zones and by measuring local polarisation curves. It is shown that individually each inhibitor has low inhibition efficiency, with CTAB reducing the corrosion rate by 62% through suppressing cathodic reactions and La(4OHcin)3·5H2O by 75% through suppressing anodic reactions. When combining the cathodic inhibitor CTAB and the anodic inhibitor La(4OHcin)3·5H2O, significant synergistic effect was achieved, enabling drastic increase of inhibition efficiency to 93%. Inhibition mechanistic interpretation through local electrochemical polarisation curve measurements and analysis is shown to be an effective tool for localised corrosion inhibitor discovery.