Influence of 1,2-diaminoethane on the mechanism of aluminium corrosion in sulphuric acid solutions

The influence of 1,2-diaminoethane (DAE) on aluminium corrosion in H2SO4 solutions (pH 3) was investigated. In pure H2SO4, rapid uniform corrosion is followed by inhibition due to the formation of stable Al-sulphate binuclear bidentate metal bound surface complexes via a ligand exchange mechanism with two neighbouring Al-OH2+ sites. Metastable pitting is also observed. DAE acts as a strong corrosion inhibitor for both uniform and localised corrosion, due to the formation of Al–DAE monodentate hydrogen-bond surface complexes either by direct adsorption of the protonated molecule on Al-OH sites or via a ligand exchange mechanism with the proton of an Al-OH2+ site.