The effect of zinc cation on the anticorrosion behavior of an eco-friendly silane sol–gel coating applied on mild steel

•Silane coating with zinc cation was developed for active protection of mild steel.•The optimum inhibitor concentration was determined via EIS and surface analysis.•The inhibition mechanism of zinc cation in 0.1M NaCl solution was studied.•No effect of zinc cation on the film thickness and condensation reaction was shown.•A protective film was formed on the surface exposed to the inhibited NaCl solution. To provide active protection of mild steel, an eco-friendly silane sol-gel coating with ZnCl2 as zinc cation source was used. The optimal concentration of zinc cation was found using electrochemical impedance spectroscopy (EIS) and surface analysis. Evaluation of EIS data indicated that the superiority of doped-silane is mainly attributed to the corrosion inhibitive function of zinc cation at interface. Zinc cation showed no effect on the thickness and hydrophobicity of coatings which were evaluated by FESEM and water contact angle, indicating no influence on condensation reactions. Using electrochemical techniques and surface analysis, an insight into the zinc cation inhibition mechanism was obtained in the absence of silane coating. In the presence of zinc cation, FESEM/EDS indicated precipitation of a layer composed of zinc hydroxide and/or oxide on the mild steel surface.