Conservation of corroded copper alloys: a comparison of new and traditional methods for removing chloride ions

Abstract

A comparison of new and traditional methods for stabilizing corroded copper alloy artifacts is presented, using data obtained from a variety of objects from both marine and land-based sites. The data show that there are common parameters that determine the rate at which chloride ions are removed. The choice of methods is discussed in terms of cost effectiveness and what patination changes are acceptable. The seven washing regimes, ranked in order of the rate of removal of chloride ions, show that alkaline dithionite is very much faster than thiourea-inhibited citric acid solutions, than 5 wt% sodium sesquicarbonate than 1 wt% benzotriazole than 50 vol% acetonitrile than 1 wt% sodium sesquicarbonate than distilled water. The effectiveness of the treatments in preventing ‘bronze disease’ is also discussed.