Study On The Silanization Treatment Of Aluminum Alloy And Magnesium Alloy

Silane technology have been rapidly developed in the field of corrosion control of metals as one of the"green"replacements for conventional chromating, recent years. This technology is based on the characteristic of silane which can be hydrolyzed to silanol which can interact with metal oxide, and have self-condensation.The films can be prepared by electrodeposition or dipping, which offers not only corrosion protection of metals but also stable adhesion to abroad range of paints.In the foretime, many import research achievements in silane technology have been obtained and parts of them have been applied to corrosion protection of metals in industry, such as galvanized steel.However, Up to now the technology still have many issues for solving, for example: the films are too thin, easy hydrolysis, non-homogenization. The films can't protect aluminum alloy and magnesium alloy, which can be corroded easily.In the study, assistant deposition agents and modifying agent is added into silane solution, in order to optimize conditions of preparation, the thickness, the compactness, the structure of films and enhance corrosion protection of metals. The results are as follows:1,Bis-1,2-[triethoxysilylpropyl]tetrasulfide (BTSPS) films have been successfully deposited at low cathodic potential in silane solution modified by surfactant, and a new critical cathodic potential (NCCP), -1.6 V has been found. Electrochemical impedance spectroscopy (EIS) tests and polarization curves indicated that BTSPS films prepared at low cathodic potentials in modified silane solution exhibited obviously higher corrosion resistances in comparison with silane films prepared by conventional electrodeposition method. The scanning electron microscopy (SEM) images indicated the surface morphology of silane films prepared at low cathodic potential were more compact and thicker than those prepared at conventional critical cathodic potential (-0.8V).Hydrogen evolution could be decreased as well as the electrodeposition of silane could be improved while adding the surfactant.2,Modifying agent B is added into silane solution in order to modify the structure of films prepared by dipping. Electrochemical impedance spectroscopy (EIS) tests and polarization curves indicated that the polasization resistance and the pore resistance of the films is higher than that of the films prepared in pure silane solution. Fourier Transform Attenuated Total Reflection Infrared Spectroscopy(FTIR-ATR) show that chemical structures and characteristics of films modified by modifying agent B have occurred, which imply that the modifying agent B have been successfully doped into the films. In the experiment, 9.7 mass % the modifying agent is optimum, the corrosion protection of metals coated by the modified films is best.