In this study, the effect of curing on the structure and protective performance of an eco-friendly silane solgel coating on stainless steel 304L was investigated using electrochemical methods as well as surface analysis. The hybrid film consisting of tetraethoxysilane, methyltriethoxysilane and g-glycidyloxypropyltrimethoxysilane was applied on the substrate via a sol-gel route. The electrochemical noise data indicated that the corrosion of stainless steel in a 3.5% sodium chloride solution is more effectively prevented through application of a coating cured at a higher temperature for a longer time.According to the Fourier transform infrared spectroscopy spectra, field emission scanning electron microscopy images and water contact angle analysis, the behavior was attributed to the formation of a highly crosslinked siloxane network by increasing the curing time and temperature. Consistent with the results of electrochemical noise measurements, electrochemical impedance spectroscopy data showed the significant effect of curing time and temperature on the hybrid silane film structure. Fig. 1 Time records of electrochemical current noise for samples (a) S7 (b) S3 after 7 days of immersion in 3.5 wt% NaCl solution. 43228 | RSC Adv., 2015, 5, 43225-43233 This journal is

Propose This paper aims to access the protective function of hybrid sol-gel coatings deposited on 304L stainless steel substrate in silane solutions containing a mixture of tetraethoxysilane, methyltriethoxysilane and glycidyloxypropyltrimethoxysilane with different pH values during various immersion periods. Design/methodology/approach The 304L stainless steels coated through 10 and 30 s of immersion in the silane solutions with pH values of 2.1 and 2.8 were exposed to NaCl solution. The corrosion resistance of the coated substrates was studied through taking advantage of electrochemical noise method as well as atomic force microscopy (AFM), water contact angle and field emission-type scanning electron microscopy (FESEM) surface analysis. Findings The electrochemical current noise, PSD (I) plot, noise resistance and characteristic charge as parameters extracted from electrochemical noise method indicated the superiority of eco-friendly silane coating deposited on the substrate surface during 10 s exposure to the solution, due to the film uniformity and homogeneity as confirmed by FESEM and AFM. Moreover, immersion of the stainless steel in the silane solution with pH 2.1, characterized by higher hydrolysis ratio, led to more effective corrosion control in the NaCl electrolyte according to the results of electrochemical noise and FTIR measurements. Research limitations/implications The noise resistance and characteristic charge as electrochemical noise parameters were only used in this research to evaluate the protective behavior of the water-based silane sol-gel coatings. Future studies should examine the correlation between electrochemical noise data and the parameters extracted from other electrochemical methods, e.g. electrochemical impedance spectroscopy. Practical implications The data obtained in this research may provide an effective approach based on electrochemical noise method to screen the silane sol-gel coatings for protection of metallic substrates against corrosion. Originality/value According to the literature, no report can be found studying the effect of immersion time on a silane solution, including glycidyloxypropyltrimethoxysilane, tetraethoxysilane and methyltriethoxysilane, as well as the silane solution pH on the corrosion resistance of 304L stainless steel in NaCl solution through electrochemical noise method.