Super-hydrophobic multilayer coatings with layer number tuned swapping in surface wettability and redox catalytic anti-corrosion application

Abstract

The wetting characteristic of a metal surface can be controlled by employing different coating materials and external stimuli, however, layer number (n) modulated surface swapping between hydrophobicity and hydrophilicity in a multilayer structure to achieve prolonged anti-corrosion ability was not taken into consideration. In this study, we proposed a layer-by-layer (LbL) spin assembled polyaniline-silica composite/tetramethylsilane functionalized silica nanoparticles (PSC/TMS-SiO2) coating with the combined effect of super-hydrophobicity and enhanced anti-corrosion ability. Interestingly, the hierarchical integration of two coating materials with inherently different surface roughness and energy in a multilayer structure allows the wetting feature to swap from hydrophobic to hydrophilic state by modulating n with decreasing hydrophilicity. The samples with odd n (TMS-SiO2 surface) are hydrophobic while the samples with even n (PSC surface) exhibits the hydrophilic character. The TMS-SiO2 content was optimized to achieve super-hydrophobic coating with significantly high water contact angle (CA) 153° ± 2° and small sliding angle (SA) 6° ± 2°. Beside its self-cleaning behavior, the electro-active PSC/TMS-SiO2 coating also exhibits remarkably enhanced corrosion resistance against aggressive media. The corrosion resistance of the coating was remained stable even after 240 h of exposure, this enhancement is attributed to super-hydrophobicity and anodic shift in corrosion potential.

A Solution-Processable, Nanostructured, and Conductive Graphene/Polyaniline Hybrid Coating for Metal-Corrosion Protection and Monitoring

“…9 , with GPn-Cu, P-Cu, and B-Cu exhibiting equilibrium contact angles of 98 ± 2°, 69 ± 2°, and 52 ± 3°, respectively, indicating that the GPn coating renders the copper surface hydrophobic, which can be attributed to the microstructural and inherent chemical properties of GPn. All corrosion-related ionic and molecular species are soluble in water and the hydrophobic nature of the GPn layer will contribute to protecting the copper metal in aqueous phases 32 .

Figure 9 Water-droplet contact-angle test on ( a ) GPn-Cu, ( b ) P-Cu, and ( c ) B-Cu.

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A Review of Fabrication Methods, Properties and Applications of Superhydrophobic Metals

“…Layer-by-layer (LbL) deposition is a powerful tool for polymer surface modification [113] and has been employed in many reports in the literature [114,115]. Concerning the LbL deposition on metallic substrates, a representative work is the one by Syed et al [116]. They proposed a layer-by-layer, spin-assembled coating, made of a polyaniline-silica composite, coupled with tetramethylsilane (TMS) functionalized silica nanoparticles (PSC/TMS-SiO 2 ) (Figure 16).…”

Exploring corrosion protection properties of alkyd@lanthanide bis-phthalocyanine nanocomposite coatings

“…This means that LnPc 2 particles decrease the contact of the coating surface with the corrosive solution leading to an improvement in the anticorrosion behavior of the coatings. 27 Fig. 8 displays the results of the thermogravimetry analysis (TGA) of the studied coatings.…”