In Situ Evaluation of the Protective State of Patinas Developed on Copper Alloys in Urban Environments

The present work analyze the protective state of patinas developed on bronzes of different composition, which are the base alloy of outdoor exposed monuments in Buenos Aires city. The results of in situ measurements and X-ray energy dispersion (EDX) analyses, carried out on powder samples of different sectors and metallic micro-samples of pre-selected zones, were used to select the best intervention criteria to be applied on two historical-national monuments: Adolfo Alsina and El Cristo Central monuments. It could be established that chemical composition and morphology of the samples, as well as their colour and texture, are directly related to the exposure grade of the selected area of the monument, to the effect of pollutants and atmospheric agents. Bearing in mind these results, and those of measurements of temporal variation of the corrosion potential by means of a technique applied in situ, sectors« intervention was proposed, maintaining the protective patinas and respecting the state in which the works are at the present time, in reference to the moment of their outdoor exposure.