Antifouling coatings for underwater archaeological stone materials

This research is part of the Italian national project entitled COMAS (Planned COnservation, in situ, of underwater archaeological artefacts), concerning the degradation phenomena occurring during the permanence of archaeological items in underwater environment and their conservation in situ by means of new methodological approaches. One of the activities within the project was devoted to the formulation and testing of products for the conservation of stone materials against biofouling, which is the most aggressive degrading agent in underwater environment. This research has been focused on the application of metal oxide nanoparticles on stone surfaces. They have been dispersed in siloxane wax in order to bond the nanoparticles to the stone, and to make it possible to apply the mixture directly underwater. Several formulations have been prepared, applied on marble specimens, and tested in laboratory to check the hydrophobicity and the colorimetric variation induced by the products. Moreover, treated specimens have been hold in underwater environment for two years, to study the bio-colonization on treated surfaces. The underwater archaeological park of Baia (Naples, Italy) in the area of the Villa con ingresso a protiro, has been chosen for the in situ tests. Transmitted light optical microscopy and scanning electron microscopy (SEM) coupled with microanalysis (EDS) were used to study the biological colonization and the interactions with treated and untreated stone specimens, observed in different exposure periods. Results showed a significant slowdown of the biological colonization on treated surfaces. (C) 2016 Elsevier B.V. All rights reserved.