Evaluation of nanostructured coatings for the protection of apuan marble stone

Abstract

Nowadays the use of multifunctional nanomaterials has significantly increased with interesting applications for the cultural heritage conservation sector, leading to the definition and use of products with innovative properties. Therefore, a preliminary validation of the performances and behavior over time of these treatments becomes an unavoidable key point for a correct use of these products before being applied to historical materials, in order to avoid irreparable damage over time. In this direction, the aim of this study was to evaluate the effectiveness of the treatment with multifunctional nanostructured products on Apuan marble. The focus of the work was to test methods to accelerate aging, in order to simulate different environmental agents of degradation to which marble in historical buildings can be exposed. Stone samples were examined after exposition to high temperature cycles in a muffle furnace, treatments in saline solution, cycles of thermal shock and aging by SO2 action in presence of humidity. After each artificial aging cycle, resulting changes in appearance were noticed and chemicalphysical properties were measured in order to compare differences between fresh and treated samples. The protective qualities of the coatings were evaluated using the following tests: contact angle; photocatalytic properties by methylene blue degradation tests; photodegradation kinetics of pollutants under UVA irradiation. Before and after the treatments, scanning electron microscopy equipped by microanalysis detector (SEM-EDS) was also used to evaluate changes in the surface morphology of the samples. The results showed effects of degradation in the rock samples due to aging after each test and all the products applied to the sample surface seemed to be very efficient in relation to their functions.