Procedimientos de protección frente a la oxidación de sulfuros metálicos en pizarras para techar

Abstract

This thesis describes efficacy results for several protective treatments applied to roofing slate to reduce the oxidation of sulphide inclusions and so resolve a major conservation problem for ornamental rock in buildings and monuments. Different silane-siloxanes and acrylic-based formulations, some with corrosion inhibitors, were applied by spray and immersion at different concentrations. The effectiveness of the treatments was evaluated by measuring the static contact angle and variations in the water absorption coefficient. Also evaluated was the durability of the treatments with respect to thermal cycles, ultraviolet light and colour variations caused in the rock by the products. In all the cases, product consumption was very low, due to the pore system in the tested rocks. Furthermore, no treatment increased the static contact angle above 90°. However, three products considerably increased sulphide resistance to oxidation during thermal cycles. The commercial silane-siloxane products are possibly best suited for future industrial application, as they do not cause significant changes in rock colour and are reasonably resistant to ultraviolet light. Studied in a second phase was the interaction between the protective products and iron sulphides and the durability of this interaction using various analytical techniques: Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and electron microscopy, among others. This research phase aimed to underpin the technological perspective of this thesis with scientific knowledge regarding slate and iron sulphide behaviour in response to different types of oxidation inhibitors.