Protocol for assessing the effectiveness of protective coatings for roofing slate

Abstract

Spain is a world-wide leader in roofing slate production, quarriying more than 600,000 tons of slate of great quality and generating around 300 euros million in sales each year. However, an enormous quantity of slate plates is considered as a low quality product or discarded every year as waste. The application of protective products on roofing slate tiles helps to commercialise slate with higher oxidation rates, reducing wastes and environmental problems. The present protocol serves to evaluate the new protective products that are now used by slate producers. A combination of three technological tests is proposed here, along with a visual questionnaire to grant quality indices. Each test is oriented to clarify critical properties for the future use of the roofing slate, as follows: (i) Thermal cycles were used to determine the oxidation rate of iron sulphides; (ii) Slate behaviour in acid urban atmospheres was interpreted by exposition of slate tiles to SO2 gas; (iii) Effectiveness of the protective layer under saline corrosion and solar radiation was obtained by exposition to saline fog and UV-irradiation.

España es líder mundial en producción de pizarras detechar; la producción supera las 600.000 toneladas depizarra de gran calidad, suponiendo más de 300 millonesde euros. La aplicación de la pizarra con productos pro-tectores permite comercializar placas más oxidablesreduciendo escombreras y problemas ambientales. Elpresente protocolo sirve para evaluar estos nuevos pro-ductos protectores que empiezan a utilizarse en el sectorpizarrero. Se propone una combinación de tres ensayostecnológicos junto con un cuestionario visual para otor-gar índices de calidad. Cada ensayo está orientado paraclarificar una propiedad importante en el uso de la piza-rra de techar: (i) Ciclo térmico para determinar el gradode oxidación de los sulfuros de hierro; (ii) Exposición algas SO2para conocer su comportamiento en ambientesurbanos ácidos; (iii) Exposición a la niebla salina y rayosUV para evaluar la eficacia de la capa protectora frente ala corrosión salina y la radiación solar.