One-step fabrication of robust and durable superamphiphobic, self-cleaning surface for outdoor and in situ application on building substrates

Hypothesis: Water and oil inhibition treatment is essential for protecting natural and artificial stone surfaces. Bioinspired super-antiwetting surfaces with “lotus effect”, together with superoleophobic properties, can be achieved combining very low-surface-energy materials and suitable surface roughness. Exploiting the natural roughness of stone surfaces, the simple and inexpensive fabrication of superamphiphobic surfaces through the coating dispersion deposition is expected. It seems the ideal method for the safeguard of contemporary and historical constructions, since the physical, chemical and aesthetic properties can be maintained. Experiments: The new coating agent (3-perfluroether-amidopropylsilane) was synthesized via one-step amidation. Hydrophobicity, robustness and environmental durability were systematically studied on stone surfaces through several tests: contact angle (CA), contact angle hysteresis (CAH), water inhibition efficiency, vapor diffusivity, chemical and mechanical resistance, artificial and field-exposure ageing. Findings: The as-prepared coating demonstrated superamphiphobicity (oil and water CA > 150° with CAH < 10°) on stones with low and high porosity. Moreover, it manifested very high water inhibition efficacy while maintaining high vapor diffusivity and aesthetic properties of substrates. The superhydrophobic coating showed good robustness towards corrosive chemical agents, peeling, mechanical abrasion, water immersion and environmental weathering, thereby permitting various outdoor applications, including stone protection in rainy regions where acid rain is also present.