Abstract
Museum objects made from metals face the challenge of delaying corrosion in exhibition rooms, showcases and holdings. This study examined some innovative solutions used to protect such items based on sol-gel coatings doped with lanthanum. These coatings were prepared from sols based on TEOS as a precursor. Lanthanum acetate/nitrate was added as a doping agent and corrosion inhibitor. The coatings were deposited upon slabs of copper, bronze, lead and steel, since they are among the most common metals present in museums items. The coatings application was accomplished by immersion-extraction, and the remaining sols were gelled and characterized by Fourier transformed infrared spectroscopy and differential thermal analysis and thermogravimetry. To evaluate the behaviour and resistance of the coatings, tests of accelerated aging were carried out in climatic and Kesternich chambers, as well as under an atmosphere saturated with organic acids and under UV irradiation. The simulated conditions tested were undertaken to approach real conditions inside a conventional museum showcase. The microstructure of the coatings before and after accelerated aging tests was observed through optical and field emission scanning electron microscopies. The results indicated that these coatings can be a useful preventive, conservation avenue to protect copper, bronze and lead items exhibited in museums.
Highlights
Many museum objects and collections are composed of metals and alloys or, at least, have metallic components
Protection procedures, patination techniques and paint systems commonly used for modern metals and metallic objects cannot be applied with any guarantee of safety to historical materials and museum items [2,3]
differential thermal analysis (DTA)-thermogravimetric analysis (TGA) results pointed out the additional improvement provided by the incorporation of La3+ -ions into the sol-gel silica network, since a progressive delay of the thermal evolution of the sol-gel matrix occurs, which extends the range of the thermal activity of dopants to face the corrosive processes to be produced and mitigated
Summary
Many museum objects and collections are composed of metals and alloys or, at least, have metallic components. The conservation of metals is critical to guard against the threat of corrosion, degradation and loss of material from the objects [1]. Since the thermodynamic trend of metal corrosion cannot be avoided, strategies to delay it as far as possible must be enhanced and investigated. Protection procedures, patination techniques and paint systems commonly used for modern metals and metallic objects cannot be applied with any guarantee of safety to historical materials and museum items [2,3]. This is because such items need nonaggressive products, easy application and reversibility as far as possible. Low-cost protective materials are preferred since museums budgets are limited
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