Inhibition of copper corrosion in a simulatedcooling water by pyrophthalone compounds

Abstract

The inhibiting action of some alpha and gamma pyrophthalone compounds on the corrosion of copper has been studied in a simulated cooling water (SCW) with a low pH. Corrosion tests and polarisation measurements were carried out at 20, 40, and 60°C. The pyrophthalones retard active copper dissolution and formation of Cu₂0 on a surface as well as oxygen reduction. Gamma derivatives show a higher degree of protection in comparison with alpha derivatives. The alpha derivatives form a film of insoluble complexes on the surface but with poor protective properties. It has been demonstrated that gamma pyrodiphenone is a highly effective inhibitor for general and pitting corrosion up to 60°C in SCWand provides protection comparable to that of mercaptobenzothiazole. X-ray photoelectron spectroscopy and SEM studies suggest formation of a film of polymeric structure by coordination of gamma pyrodiphenone with CU20 on the surface.