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.
Highlights
Corrosion is a thermodynamically pivotal process which consumes 3% of the world gross domestic product (GDP) annually[1, 2]
The presence of bands related to PANI and SiO2 in PANI-SiO2 Composite (PSC) spectra implies the formation of the PSC composite (Fig. S1b) and Fig. S1e shows the surface modification of SiO2 particles with HDMS
The long-term Electrochemical impedance spectroscopy (EIS) results reveal that the high corrosion resistance of the coating is stable even after 240 h of immersion in 3.5% NaCl and no drastic degradation was observed as compared to uncoated samples
Summary
Corrosion is a thermodynamically pivotal process which consumes 3% of the world gross domestic product (GDP) annually[1, 2]. It is strongly desired to develop a defect free coating with the combined effect of super-hydrophobicity and CP redox catalytic ability for long term corrosion protection of SS by a facile coating technique which provides a control over surface wettability. Our proposed strategy has several advantages such as, the co-assembly of two materials PSC and TMS-SiO2 with different surface roughness and energy in a multilayer fashion would allow layer number (n) to act as a switch to modulate surface wettability; the change in hydrophobicity to hydrophilicity can be controlled over a wide range; n can be used to control the swapping and this control is tunable to achieve self-cleaning ability; the super-hydrophobic coating with redox catalytic ability twofold the corrosion performance of metals for a long period of time due to enhanced barrier ability
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