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Materials such as wood, textiles, or plastics that are part of the exhibition system in museums are known to emit pollutants such as organic acids. Scientific and technical objects that include these materials in their composition can themselves be a potential source of emissions, which, together with inappropriate humidity and temperature conditions, can lead to corrosion of the metallic parts. In this work, we have studied the corrosivity of different locations in two venues of the Spanish National Museum of Science and Technology (MUNCYT). Coupons of the most representative metals from the collection were placed in different showcases and rooms for 9 months. The corrosion of the coupons has been evaluated in terms of the rate of mass gain, colour changes and characterisation of the corrosion products. The results were correlated to the relative humidity and concentration of gaseous pollutants to determine which metals are most susceptible to corrosion. The results show that metal artefacts exposed in showcases have a higher risk of corrosion than those exposed directly in the room, and that some pollutants are emitted by the artefacts. The corrosivity of the museum environment is low for copper, brass, and aluminium in most locations; however, some placements present a higher aggressivity for steel and lead, due to the high humidity and the presence of organic acids.

This paper presents results on the protective properties of different coatings over metals representative of those found in scientific–technical heritage collections. An examination of several objects in the collection of the Spanish National Museum of Science and Technology have allowed the identification of brass and steel as the most representative metals, and the existence of coatings (mainly shellac and acrylic resins) applied for aesthetic and/or conservation purposes. Based on these findings, brass and steel coupons coated with Paraloid B-44, B-48, B-67, B-72, Incralac, Cosmolloid H80, B-72 + H80 double layer and shellac have been studied to carry out a first screening in order to select the most promising candidates and determine the most appropriate methodology and key factors for the study. Coatings have been aged up to 336 h using cycles of UV light and water condensation. The change in the aspect of the coupons has been assessed via visual examination, optical microscopy and colorimetric measurements, with B-44 and Incralac showing the least change. EIS has been used for a quantitative evaluation of the protective properties and FTIR to measure chemical changes experienced by some coatings, such as B-48 and B-67. These evaluations allowed us to follow, understand and compare the behaviour of the different coatings and substrates after artificial ageing.