Diphenyl disulfide derivatives as high-efficiency corrosion inhibitors for copper in sulfuric acid: Experimental and theoretical studies

Three organic small molecules, namely Diphenyl disulfide (PDS), 4,4′-Dithiodianiline (DDA), and 4-Methylphenyl disulfide (MDS), were subjected to corrosion screening on copper substrates. Electrochemical testing revealed their corrosion efficacy, with MDS exhibiting the highest efficiency at 98.9 %. Investigation into MDS's corrosion mechanism attributed its superior performance to the presence of hydrophobic methyl groups, facilitating the formation of a denser molecular protective film on the copper surface. The adsorption of corrosion inhibitors on copper surfaces was investigated by Langmuir monolayer adsorption model and X-ray photoelectron spectroscopy. Theoretical calculations further elucidated the inhibitory mechanisms of these sulfurized compounds and the influence of different functional groups on corrosion efficiency. Specifically, the introduction of methyl groups enhanced MDS's ability to displace water molecules on the copper surface, thereby augmenting its corrosion inhibition potential. These findings align with the observations from electrochemical and surface analyses, affirming the efficacy of MDS in mitigating copper corrosion.