Research On The Preparation And Properties Of Composite Silane Films Deposited On Cold-rolled Steel

The phosphate surface treatment technology was mainly used in traditional corrosion surface treatment of metal materials. Owing to its high energy consumption, environment pollution, its application is limited. Thus it is necessary to investigate low-energy consumption, environment-friendly surface treatment technology for replacing the traditional phosphate processing technology. Silane surface treatment technology with low power consumption and environment-friendly features possesses a wide range of applications. But the films prepared by the ordinary silane surface treatment have lower corrosion resistance than that of the phosphate film due to the pores and cracks in the surface of the films. In this paper, the one and two-layered composite film were prepared on the cold rolled steel substrate in order to improve the corrosion resistance of ordinary silane film. And the microstructure, composition and corrosion resistance of these films were also investigated.The main work of this paper is as follows:(1) Ordinary silane films were prepared on the metal substrate and deposition process were optimized in this paper. The results of EDS and XPS show that C, O, Si, Fe exist in ordinary silane film. This indicates that the silane films formed on the surface of metal substrate SEM results show that the films are thin. The results of corrosion resistance show that the corrosion resistance of ordinary silane films is lower than that of phosphate film.(2) One layered composite films were prepared on the surface of metal substrate by doping fluorozirconic acid to the silane solution. The results of the corrosion resistance show that, with the increase of the added amount of fluorozirconic acid, corrosion resistance increase firstly, reach the maximum, then decreases gradually. The doping amount of fluorozirconic acid corresponding to the highest corrosion resistance is 1 × 10-3 M.The corrosion resistances of one layered silane film was significantly improved compared with ordinary silane film and phosphate films. XPS and EDS results indicate that the silane composite film contains C,0, Si, Zr, indicate that several elements are involved in the deposition process of the film. SEM results indicate that one layered composite film have completely covered the metal substrate.(3) First lanthanum salt conversion films were prepared on the surface of cold rolled steel substrate, then y-GPS silane films were deposited in order to prepare two layered composite films. The deposition processes of two layered composite films were optimized. EDS results indicate that the two layered silane composite film contains C, O, Si, La, indicate that several elements are involved in the deposition process of the film. XPS results shows that the composite films are composed of the inner and outer film. Fe, La are involved in the deposition process of the inner film. C、O、Si are involved in the deposition process of the inner film and outer film. The results of corrosion resistances show that the corrosion resistances of two layered films are higher than the one layered composite film,the ordinary silane films and phosphate films.