Non-destructive surface analysis of accelerated corroded copper alloys

Purpose - The purpose of this paper is to investigate the surface corrosion products of copper alloys by non-destructive techniques (NDT) and correlate them with their bulk composition. Design/methodology/approach - Specimens of copper alloys, whose compositions were close to those of ancient copper-based artefacts, were left to be corroded in simulated soil solution containing ammoniacal buffering solution of pH = 10 in 1:1 ratio, in order to accelerate the corrosion rate. The elemental compositions of the surface corrosion products were determined versus time using X-Ray Fluorescence Spectroscopy, and the surface morphology by Scanning Electron Microscopy with Energy Dispersive X-Ray Micro-detector methods, and the results were compared to the bulk composition, as measured by Atomic Absorption Spectroscopy and Inductively Coupled Plasma Atomic Emission Spectroscopy. Findings - During the corrosion evolution of the copper alloys in the corrosive solution, transitional phenomena were observed such as an initial decrease of the copper concentration with a simultaneous increase of the concentrations of the secondary alloying metals (Sn, Zn and Pb). After 30-60 immersion days, the alloy concentrations were stabilised. Originality/value - The results of this research could contribute to the non-destructive characterisation of copper-based ancient artefacts (from which the taking of samples is not allowed).