Bioorganic compounds as copper corrosion inhibitors in hydrocarbon media

► The corrosion protection of Cu in oil by four bioorganic compounds was examined. ► Utilising the techniques of ellipsometry, AAS and a standard IEC corrosion test. ► It was concluded that adenine and purine exhibited a surface passivating effect. ► Cysteine and histidine did not exhibit a surface passivating effect. The corrosion protection of copper by four bioorganic compounds; adenine, purine, cysteine and histidine, in hydrocarbon media has been examined by in situ ellipsometry, atom absorption spectroscopy and a standard corrosion test. Adenine and purine were found to irreversibly bind to the copper surface. The amount of dissolved copper was severely lowered and the copper surface appeared unaffected. It was concluded that adenine and purine exhibited a surface passivating effect, whereas the effect of cysteine and histidine was significantly lower. The influence on oxidation stability of the medium by addition of the compounds was examined and found to be minor.