An Al-Cu Multielectrode Model for Studying Corrosion Inhibition with Praseodymium Mercaptoacetate at Intermetallic Particles in AA2024

Abstract

Dealloying of S-phase particles on AA2024-T3 leave behind highly cathodic Cu-rich particles, creating a galvanic corrosion environment. Clustering of these particles intensify localised dissolution of adjacent matrix leading to pitting. Evaluation of such galvanic activities is critical to develop effective corrosion inhibitors. Unfortunately conventional electrochemical methods are unable to probe this type of anodic attack because in principle they only evaluate general corrosion and cannot measure galvanic corrosion currents flowing between particles and adjacent matrix. This work uses a multielectrode composed of four copper and forty-four aluminium electrodes to model galvanic activities occurring over a cluster of dealloyed S-phase particles to better understand localised attack and at clustered sites. The model Al-Cu multielectrode was shown to be an effective tool to investigate local interactions between Cu electrodes and Al electrodes which undergo significant anodic current densities, simulating the anodic attack on the aluminium matrix of AA2024-T3. Additionally this tool can more strictly differentiate between inhibitors for localised corrosion control. An environmentally friendly rare earth corrosion inhibitor, praseodymium mercaptoacetate (Pr(MAcet)3), has been evaluated by this technique and has been found to rapidly reduce anodic current densities at a faster rate than PrCl3 when concentrations were sufficiently high (>10−3 M).