Characterisation and properties of synthetic patina on copper base sculptural alloys

Copper-based statuary alloys were submitted to accelerated patina formation and degradation in well-defined laboratory conditions. Analogies and differences between these patinas and patinas developed on monuments during long-term outdoor exposure are discussed. A very simple patina growth and degradation technique is proposed to better understand the electrochemical processes involved. Patinas were analysed in many replica samples and using destructive techniques not applicable to monuments due to their historic and cultural value. The best quantitative information obtained by "in situ" open circuit potential and current density measurements demonstrated the significant contribution of these electrochemical tools to Cultural Heritage maintenance.