Protective Coatings for Metals in Scientific—Technical Heritage: The Collection of the Spanish National Museum of Science and Technology (MUNCYT)

Abstract

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.

Corrosion Risk to Metal-Based Artefacts in a Scientific and Technical Museum: An Assessment of Environmental and Exhibition Conditions

“…Lead, copper, aluminium, carbon steel, and brass were selected as the most representative metals in this collection [ 21 ], and coupons acting as metal dosimeters, were prepared based on the methodology of ISO 11844-2 [ 19 ]. These coupons are used to evaluate the corrosion experienced by each metal after its exposure in different locations of the museum (showcases and rooms) with different methods: measuring the rate of mass increase and classifying the corrosivity of the environment for each metal, evaluating the colour changes experienced, and characterising the corrosion products formed on the coupons by XRD.…”

Present Status and Perspectives of Graphene and Graphene‐related Materials in Cultural Heritage

“…Microcrystalline waxes represent another viable option, under both outdoor and indoor exposure conditions, but their long-term durability raises major concerns. [63] The addition of anti-corrosion compounds is, A) Illustration of the potential applications of graphene and graphene-related materials in cultural heritage; B) Chemical structure of graphene, graphene oxide, and reduced graphene oxide, with a focus on the different functional groups; C) Classification of the different graphene types according to the number of layers, the average lateral dimension, and the atomic carbon/oxygen ratio. Reproduced with permission.…”

“…Natural and synthetic waxes are commonly employed for providing protection against external harmful agents, representing an important tool for restorers, particularly in view of their ease of application. [ 63,64 ] However, their effectiveness against corrosion is significantly limited, particularly in the case of metal artifacts in outdoor environments. Microcrystalline waxes represent another viable option, under both outdoor and indoor exposure conditions, but their long‐term durability raises major concerns.…”

“…Microcrystalline waxes represent another viable option, under both outdoor and indoor exposure conditions, but their long‐term durability raises major concerns. [ 63 ] The addition of anti‐corrosion compounds is, thus, often necessary to enhance their corrosion resistance. [ 65 ] The integration of benzotriazole, for example, is effective in hampering the corrosion of bronze artifacts by promoting the formation of a protective layer.…”

“…[ 68 ] Acrylic and vinylic polymers and co‐polymers, in particular, are commonly used as coatings, consolidants, and adhesives. [ 63,69 ] Yet, they also present issues related to long‐term stability and aging. [ 70 ] Epoxy resins are being widely employed to form homogeneous thin films over the surface of the objects to enhance their hydrophobicity.…”