Underwater Performance of Eco-Friendly Choline-Based Ionic Liquid Coatings Applied on Stone Surfaces

In the marine environment, numerous factors endanger the preservation of underwater rock surfaces as well as submerged archeological artifacts, including physical, chemical, and biological processes. Limestone and marble are common materials used in artifacts due to their availability and long-term durability. However, such surfaces provide a suitable substrate for the settlement of micro- and macro-organisms, causing so-called biofouling, which significantly contributes to stone deterioration. Previous studies have demonstrated the applicability of antifouling coatings containing ionic liquids (ILs) on marble surfaces and assessed their durability for up to 15 days under submerged environments. To further corroborate these results, additional physical studies (colorimetric, contact angles, capillarity water absorption measurements, and UV aging) were carried out on treated limestone. Washout tests were also performed on both lithotypes to verify the coatings’ stability under medium-term underwater exposures. The results of these investigations are reported here. Our data confirm that the application of IL-based coatings had no effect on the intrinsic properties of the limestone surfaces, as previously reported for marble, including resistance to daily UV irradiation. In addition, laboratory tests demonstrated good coating durability against seawater erosive action for up to 6 months.