Study On The Preparation Mechanism And Performance Of The Zr/Silane Hybrid Film On Surface Of Cold-rolled Steel

Silane surface treatment has a considerable market prospect owing to its simple process, low energy consumption and environmental friendliness. However, the silane film is thin, mechanical properties is poor and silane film does not has self-healing properties, which limit its application. Moreover, the quantitative study of hydrolysis degree of silane is important for the study of dilution of concentrated silane solution and recycling of silane in industry.In this paper, bis-[trimethoxysilylpropyl]amine(BAS) and vinyltriactoxysilane(VTAS) was used as raw materials. The main content includes three aspects:(1) the hydrolysis degree of mixed silane system was quantitatively study of using gas chromatography internal standard method;(2) the preparation process was optimized for zirconium films;(3) zirconium/silane hybrid films were prepared, the effects of immersion conditions on the open circuit potential of two electrode system were investigated, the films were characterized using polarization curves and electrochemical impedance spectroscopy; the formation mechanism of hybrid silane film was proposed, and the films were observed using scanning electron microscopy and atomic force microscopy.The concentrations of CH3 OH and CH3 COOH, as hydrolysate of BAS and VTAS, respectively, were measured accurately by gas chromatography, and then the hydrolysis degree was calculated. The hydrolysis degree of BAS/Micxy V, BAS/Industrial V and BAS/Maya V were 11.4%/29.1%, 8.4%/26.9% and 33.1%/27.9%, respectively. The experiment is confirmed further by infrared spectroscopy, polarization curves and Cu SO4 pitting corrosion. So it can be inferred that the performance of the three hydrolysis solutions follows the order: BAS/Micxy V > BAS/Industrial V > BAS/Maya V. It indicates that the method of gas chromatography can effectively and rapidly character the hydrolysis degree of silanes in BAS/VTAS system, whose results can be used as quantitative basis for the evaluation of the property of silane hydrolysis.The optimal condition for the preparation of Zr films is that immersion time is 5min, immersion temperature is 30°C, solution p H is 4 and the concentration of Zr(NO3)4 is 0.0039mol/L. The formation mechanism of zirconium/silane hybrid film in Zr(NO3)4/silane solutions is that most zirconium deposits on the surface of iron plate at the initial immersing stage, then the adsorption of silane on the residual surface dominates the following stage. This conclusion is confirmed further by the quantitative analysis of the θT of silane film in Zr film + silane film, according to the data of icorr from potentiodynamic polarization measurements. Moreover, Zr/silane hybrid film shows better corrosion resistant than pure Zr film or silane film.