Insights into the stability of fluorinated super-hydrophobic coating in different corrosive solutions

Abstract

Super-hydrophobicity is attractive due to their special functions. Fluoride reagents are widely used to fabricate super-hydrophobic coatings by reducing surface free energy. Previous papers have been extensively investigated the chemical stability of such super-hydrophobic coatings in acid, salt and alkaline solutions. However, they just described experimental phenomena by comparing the water contact angles before and after immersion into corrosive solutions. Rare work focused on the underlying reasons to elucidate the failure mechanism or protective mechanism of fluorinated super-hydrophobic coating. Therefore, this study mainly explored the influences of acid, salt and alkaline solutions on stability of super-hydrophobic surface with fluorinated coating, and then the corresponding failure and protective mechanisms were proposed. This paper revealed that the acid solution destroyed the CuO nanosheet structure, leading to the automatic removement of fluorinated coating. The salt solution had the slightly negative effect on the fluorinated super-hydrophobic coating due to pits generation and several fluoride molecules vanishment. However, the hydroxy ion in alkaline solution could promote the hydrolysis, dehydration and polycondensation reactions, resulting in superior stability of super-hydrophobicity due to tight attachment of fluoride molecules. Finally, the electrochemical experiments were conducted to provide strong support in data to further verify reasonability of the proposed explanations.