© 2016 The Authors The behaviour and molecular structure of three organic additives adsorbed from oil onto a copper surface rich in copper (II) oxide is presented. The variation in the ability of these three agents to prevent corrosion of the copper oxide surface by exposure to sulphur is also included. A combination of visible observations, X-ray photoelectron spectroscopy (XPS) and neutron reflection (NR) are used to characterise both the adsorbed layer and underlying copper oxide. The model additives are chosen to represent ‘effective’, ‘intermediate’ and ‘ineffective’ inhibitors for copper.