Comparative study of patinas formed on statuary alloys by means of electrochemical and surface analysis techniques

A comparative evaluation of natural patinas and those formed during acid rain laboratory tests was applied to predict patina stability in corrosive urban environments. SEM-EDX analyses of various statuary alloys after the laboratory tests distinguished areas of correlative intensity of attack and S percentage, depending on the alloy. Moreover, EDX and X-ray diffraction (XRD) determined the chemical composition of different coloured patina carefully scraped from a bronze monument, submitted to 75 years outdoors exposure. To analyse the electrochemical potential evolution with time the in situ Pourbaix technique was applied on the laboratory-exposed samples and over representative areas of the monument, at 2 years interval. (C) 2003 Elsevier Ltd. All rights reserved.