Preparation of superhydrophobic polyimide films modified with organosilicasol as effective anticorrosion coatings

In this study we prepared superhydrophobic polyimide (PI) hybrid coatings for anticorrosion application by adjusting their surface roughness and surface composition through spray-coating with silylated perfluoroalkylsilane-modified organosilicasol (silylated fluoro-organosilicasol), which increased the surface hydrophobicity. After silylation with 1,1,1,3,3,3-hexamethyldisilazane (HMDS), the silylated fluoro-organosilicasol further transformed the PI surface into a superhydrophobic state with a static water contact angle of greater than 160° and a low hysteresis of 10°. We examined the mechanism behind the enhancement in superhydrophobicity through analyses of the surface topology and chemical composition of the films, using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electron spectroscopy for chemical analysis (ESCA). These analyses suggested that both surface roughness and silylation of the fluoro-organosilicasol making more CF2 groups on the outmost surface rendered the surface hydrophobicity. The anticorrosion properties of these superhydrophobic coatings were also examined through Tafel measurement. These PI hybrid coatings demonstrated lower corrosion current density and nobler corrosion potential and higher polarization resistance. The enhancement in anticorrosion performance was believed to be contributed from the superhydrophobicity and dual barrier protection from the fully-covered fluoro-organosilicasol, insulating the metal from corrosive species in the medium. This superhydrophobic coating technique with good stability guaranteed better corrosion protection and also has great potential for application to other polymeric films.