The damage can occur through dissolved oxygen (or air) or corrosive forms of sulphur. Several types of sulphur are present in crude oil, some of which react with copper. As it is not easy to removal all sulphur from oil, corrosion inhibitors are often added to the oil mixture to protect copper surfaces. Previous research has concentrated on how corrosion inhibitors work in water-based mixtures, but a team of UK researchers has used X-ray photoelectron spectroscopy (XPS), plus neutron reflection on the INTER reflectometer, to study the behaviour and molecular structure of three organic additives adsorbed from oil onto a copper surface. Researchers discovered that molecules that form dense coverage on the surface do not necessarily provide greater protection compared to less dense layers, implying that the chemistry of surface binding is more important. Their results offer a greater chemical understanding of the corrosion process, and may lead to better corrosion inhibitors.
Related publication: R. J. L. Welbourn et at. “Corrosion and inhibition of copper in hydrocarbon solution on a molecular level investigated using neutron reflectometry and XPS" Corrosion Science 115 (2017), 68-77, DOI: 10.1016/j.corsci.2016.11.010