Influence of ZnO Nanoparticle Size on Barrier Performance and Corrosion Protection of Poly(dimethylsiloxane)-Coated Q235 Steel in Chloride Environment: Bode and Computational Simulation Investigations

Ethylhexanoic acid-modified PDMS-ZnO nanocoatings containing varying dimensions of ZnO nanoparticles (30, 50 and 90 nm) were prepared. The main objective was to appraise the effect of varying dimensions of ZnO nanoparticles on the protective efficacy of ethylhexanoic acid-modified PDMS coating in aqueous solution of 3.5 wt% NaCl/ Pseudomonas aeruginosa . Barrier properties and anti-corrosion performance of the coatings were evaluated by electrochemical impedance spectroscopy (EIS). Computational simulation techniques [quantum chemical computation (QCC) via density functional theory (DFT) and molecular dynamics (MD) simulation] were employed to provide molecular/atomistic level information on the chemical molecules responsible for corrosion protection performance and their adsorption phenomena. EIS results showed that the coating containing 30 nm ZnO nanoparticles maintained high impedance values in the order of 10 9 magnitude throughout the immersion periods. The obtained results were validated by wettability, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy results. The DFT calculations showed that PDMS and ethylhexanoic acid with energy gaps of 5.123 and 5.337 eV, respectively, are most responsible for the corrosion protection effect. The good adsorption of the coating containing 30 nm ZnO particles was validated by MD simulation result with adsorption energies (E ads ) of − 2.28 kcal/mol, suggesting it is most susceptible for hydrophilic interaction.