The golden alloy Cu5Zn5Al1Sn: Patina evolution in chloride-containing atmospheres

The influence of chloride deposition on the formation, evolution and barrier properties of the patina formed on Cu5Zn5Al1Sn used for architectural cladding is explored via long-term marine field exposures and laboratory investigations. The presence of Cu2O, ZnO, Al2O3 and SnO2 within the inner part of the patina and intercalation of SnO2, Zn5(CO3)2(OH)6, Zn6Al2(OH)16CO3·4H2O, Zn5(OH)8Cl2·H2O within its outer part, predominantly composed of Cu2(OH)3Cl, significantly reduce the chloride-induced corrosion compared with Cu metal. The intercalation of zinc-rich corrosion products within the patina and not at the top-surface explain their marginal influence on the runoff process that mainly occurs at the outmost surface.