Influence of nano-silica doping on the growth behavior and corrosion resistance of γ-APS silane films fabricated by electrochemical-assisted deposition

The influence of nano-silica doping on the growth behavior and corrosion resistance of γ-APS silane films fabricated by electrochemical-assisted deposition was systematically investigated by reflection absorption infrared spectroscopy, electrochemical impedance spectroscopy, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, contact angle test and neutral salt spray test. Density functional theory calculation was also applied to elaborate the adsorption behavior of γ-APS on low carbon steel surfaces. And meanwhile, the changes of surface coverage and dissolved oxygen reduction in the cathode surface over time were intensively analyzed according to the I–t curve during electrodeposition process. The experimental results revealed that the impedance values of the composite films firstly increased and then decreased with increasing nano-silica concentration, and there was a critical doping concentration about 0.4 g·L−1, under which the obtained γ-APS silane composite films presented high compactness and protective properties. Other results were highly consistent with the electrochemical results. Moreover, the hydroxyl-rich nano-silica was also involved in the chemical reactions that occurred on the metal surfaces, and the influence mechanism was proposed.