Anticorrosion and barrier properties appraisal of poly(dimethylsiloxane)–ZnO nanocoating transition from superhydrophobic to hydrophobic state

Abstract

The anticorrosion and barrier properties of poly(dimethylsiloxane) (PDMS)–ZnO nanocoating transition from superhydrophobic to hydrophobic state have been evaluated. The main objective was to appraise the durability performance of anticorrosion and barrier properties of the pristine superhydrophobic coating and its hydrophobic state after long-term exposure to marine water. Thus, water wettability, surface features, and corrosion resistance, as well as barrier performance of the 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane-modified PDMS–ZnO coating were evaluated after 15 cycles (1 h to 60 days) of immersion in 3.5 wt.% NaCl solution. The evaluations were made by use of surface analytical, physicochemical, and electrochemical techniques. The results show that the coating transformed from superhydrophobic state (after 1 h) to hydrophobic state (after 60 days). The transition was due to effect of corrosiveness of the salty water and disappearance of the surface air layer with consequent reduction in the surface roughness and increase in the porosity of the coating. Correspondingly, the value of the impedance modulus decreased from 4.257 × 109 Ω cm2 (after 1 h) to 7.175 × 108 Ω cm2 (after 60 days). The trend of coating film (Rcf) and charge transfer (Rct) resistances with immersion time was found to be somewhat stable after 40-day immersion time. The observed high values of impedance modulus (|Z|f=0.01 Hz), Rcf and Rct after 60 days of immersion clearly demonstrate that the anticorrosion property and barrier performance of the transformed hydrophobic PDMS–ZnO coating were good.