Long-term outdoor exposure of artificial copper patina based on brochantite

Abstract

A typical green layer of patina starts to cover copper in atmosphere condition, which is aesthetically acceptable and also provides protective properties. This work investigates stability of the artificial patina layer based on sulphates prepared from a gaseous phase during two-year exposure in atmosphere condition. XRD and SEM were employed to verify the composition and morphology of artificial patina. Colour and patina coverage were compared before and after exposure also. According to results after 1 and 2 years of exposure, it is possible to see changing of hydroxyl sulphates to more stable brochantite and filling pores in the patina layer. There is almost no colour change, however lower patina coverage is slightly evident due to precipitation and abrasive effect.