Jorge Oteiza is one of the fundamental artists of 20th-century Spanish art and one of its most influential. In 1992, he donated his extensive artistic legacy to the people of Navarra, which can be enjoyed in the Jorge Oteiza Museum Foundation and in various public spaces. In several squares and parks in Pamplona we find large metal sculptures exposed to harsh weather conditions, with corrosion being identified as the main cause of deterioration. As a result, successive restorations have been carried out, but these have not been re-evaluated. To assess their conservation condition, a collaboration between the Jorge Oteiza Museum Foundation and the CENIM-CSIC was established, thanks to the last call for scientific-technical access to the facilities of the Spanish node of E-RIHS. This collaboration has made it possible to use the mobile laboratory (METAL.es) in different locations in Pamplona to characterise and evaluate the original patinas or paints of 5 sculptures, as well as the composition and condition of protective coatings applied subsequently during past interventions. Electrochemical Impedance Spectroscopy (EIS) was used to analyse the corrosion resistance and protective capacity of the different patinas and coatings, which were higher in the steel sculptures painted with polyurethane and lower in the patinated bronzes. The protective capacity of the different bronze patinas could be compared, whereby the thicker patinas or zones with traces of coatings were the most protective. The thickness of the different layers was measured in a complementary way with an automatic electromagnetic induction probe to complement the information of the EIS data. IR spectroscopy in total reflection mode (FTIR-TR) showed that some of the sculptures still have traces of microcrystalline wax, applied in 2010 as a double-layer system of Paraloid B72+wax, of which the acrylic cannot be identified. With this technique it has also been possible to characterise the different patinas and corrosion products formed, in particular copper hydroxysulphates such as brochantite. On the basis of this diagnosis, future conservation/restoration measures can be carried out on each sculpture individually, according to its condition and type and establish periodic monitoring of the artworks.

Red de Ciencia y Tecnología para la Conservación del Patrimonio Cultural REAL SOCIEDAD ESPAÑOLA DE QUÍMICA (RSEQ)