Effect of Silane Coating on the Corrosion Resistance of TiO₂ Conversion Films

摘要

TiO2 conversion films were prepared on surfaces undergoing the hot-dip galvanizing (HDG) processusing titanium sulphate (Ti(SO4)2) as the titanium source and hydrogen peroxide (H2O2) as thechelating agent by a one-step impregnation method. The effect of passivation time on the morphologyand corrosion resistance of the film was investigated. The results show that a large amount of TiO2nanospheres appear on the HDG surface after a short immersion time. By increasing the immersiontime, the nanospheres are gradually covered by the ZnO/Zn(OH)2 conversion film, and some cracksappear on the conversion film. The electrochemical results reveal that the integral TiO2 conversionfilm shows better corrosion resistance, and the cracks cause the pitting of the corrosion resistance. Toimprove its corrosion resistance, the TiO2 conversion film was modified by silane to realizehydrophobic sealing, which results in obvious changes in the morphology and corrosion resistance.After modification, the gel layer covered the TiO2 conversion film, which would fill the cracks andmake the film hydrophobic. Thus, the corrosion resistance of the modified conversion film increased.The better the hydrophobicity of the film is, the better the corrosion resistance of the film is for a shortimmersion time. In addition, the corrosion resistance of the hydrophobic film is mainly determined bythe bottom TiO2 conversion film.