Interaction of triazole corrosion inhibitors with metallic and bimetallic surfaces under ideal and realistic conditions

While copper and copper based alloys generally have good corrosion resistance compared to ferrous alloys, in harsh conditions they do undergo corrosion. Molecular corrosion inhibitors can be used to combat this; an important class of corrosion inhibitors is triazoles. In this project, the interactions of several triazole compounds – benzotriazole (BTAH), tolyltriazole (TTAH), and 1,2,4-triazole – with copper and bimetallic surfaces were investigated under ideal and realistic conditions. Analytical techniques used included scanning tunnelling microscopy (STM), high-resolution electron energy loss spectroscopy (HREELS), x-ray photoelectron spectroscopy (XPS), medium energy ion scattering (MEIS), and transmission electron microscopy (TEM) with energy dispersive x-ray spectroscopy (EDS). Additionally, computational modelling using density functional theory (DFT) was done to support the experiments. It was found that the presence of zinc is very important when using BTAH and TTAH. On a single crystal surface under UHV condition with both copper and zinc present, BTAH appears to preferentially form surface structures with zinc rather than copper. In experiments using more realistic conditions, TTAH appears to form a much less effective passivation layer on brass when compared with copper and bronze. This is in stark contrast to tin, which does not significantly participate in the passivation layer on bronze. In experiments on a Cu(111) surface, TTAH was found to behave similarly to BTAH, albeit with less precise ordering; this indicates that studies using BTAH are relevant to TTAH. 1,2,4-triazole was found to form ordered structures on a Cu(111) surface, although it does so less readily than BTAH and the structures are not stable to as high a temperature.