Copper is an important industrial metal, predominantly used in electrical wiring and plumbing, as well as in power transformers. Throughout these applications, sulphur is known to be a strong corroder of copper, inducing catastrophic failure in the worst cases. Therefore, improving the understanding of how active sulphur species attack copper and how inhibitors interact with the surface can lead to better protection of these components.Through visible observations, XPS and previous neutron reflection (NR) measurements it is believed that the proportion of Cu(I):Cu(II) within the oxide at the surface has a strong influence on additive adsorption and subsequent sulphur corrosion. In this study we aim to prove this theory through in-situ measurement of changes at the corroding surface by NR.