Plasma reduction of bronze corrosion developed under long-term artificial ageing

Reference Cu-based alloy with chemical composition and micro-chemical structure similar to that of ancient alloys has been used for carrying out the artificial long-term degradation test based on chloride enriched soil (chemical + soil) degradation. The results show that such degradation procedure produces natural like “patinas” as the ones grown on archaeological artefacts, from a chemical, structural and micro-morphological point of view. Glow discharge plasma technique has been employed for the treatment of the as-corroded bronze coupons. The gradual elimination of chloride-containing corrosion products in favour of the formation of more stable species and even the complete reduction back to copper has been observed. The chemical and metallurgical features have been determined by combined use of different analytical techniques such as scanning electron microscopy with energy dispersive X-ray micro-analysis (SEM-EDS), X-ray diffraction (XRD) and optical microscopy.