A novel dioxime compound for protecting copper in neutral chloride solutions and to treat bronze disease in archaeological artefacts

Abstract

This study aimed to evaluate (4,6-dihydroxy benzene-1,3-dicarbaldehyde dioxime (DBDD)) as a novel corrosion inhibitor for protecting copper in neutral sodium chloride (NaCl) solutions and conserving archaeological copper-based artefacts suffering from bronze disease. Potentiodynamic polarisation techniques showed that DBDD was effective in inhibiting copper corrosion in 3.5 wt. % NaCl solution. An Iron Age copper-based fibula was used for testing DBDD; X-ray diffraction (XRD) analysis showed that it was suffering from bronze disease before treatment was initiated. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared (FTIR) spectroscopy investigations showed that DBDD coordinated with copper ions in the corrosion products and formed a protective film on the surface. Investigating the interaction of DBDD with pure copper chloride and carbonate minerals representing corrosion products appearing on archaeological artefacts proved the formation of new passive species between DBDD and these minerals. The fibula treated with DBDD showed no signs of corrosion after exposure to high relative humidity. It was concluded that DBDD was effective in protecting copper exposed to a neutral chloride-containing environment and passivating corrosion products appearing on heavily corroded archaeological artefacts suffering from bronze disease.