Translucent superhydrophobic coating for murals protection

Abstract

This study aims to protect murals by a translucent and superhydrophobic coating using a one-step spraying process, which offers simplicity, efficiency, and cost-effectiveness, while preserving the mural's visual appeal and safeguarding against moisture. Despite numerous advancements in cultural relic conservation, the application of super-hydrophobic coatings for mural preservation remains a novel approach. The coating consists of acrylic resin (Paraloid B72), nano-silica, and polydimethylsiloxane (PDMS). The optimal amounts of silica and PDMS were 3 g each in a basal solution containing 12 g of acrylic resin dissolved in 88 mL of xylene. The resulting composite coating displayed exceptional water repellency, as indicated by a contact angle of 165.5° and a rolling angle of approx. 7°. As a result, the moisture absorption of the mural decreased significantly from ∼53% to ∼5% after the application of the superhydrophobic coating. The coating had minimal impact on the water vapor permeability of the mural, with a ca. 13% decline rate. The coating is translucent with a visible transmittance of approximately 60%. Therefore, the coated mural maintains its original appearance with minimal changes. Furthermore, the superhydrophobic properties of the coating remain intact even after undergoing five cycles of high-low temperature fatigue tests, 196 hours of ultraviolet irradiation, or seven cycles of sand impacting.