Factors affecting the dissolution of copper in transformer oils

The effect of addition of acids, peroxides and model N‐containing compounds to the oils on the rate of the copper dissolution from a copper strip into the oils was studied. The oils used were poly‐alpha‐olefin 2 (PAO‐2) and a highly refined naphthenic oil. Acids and peroxides were found to increase the copper dissolution into the oil, whereas the model nitrogen‐containing compounds exhibited a surface passivatory effect. The presence of the oil's partial oxidation products was found to increase the dissolution of the copper into the oil. The reasons for these observations are discussed. The relative contribution of the electrochemical and chemical processes to the copper corrosion is discussed.