| Currently, the two most commonly used metal surface treatment methods are transforming chromate passivation and phosphate, but both methods have serious environmental pollution problems, chromated hexavalent chromium ions with a more strong carcinogenicity, serious harm to human health, and phosphate conversion of wastewater and waste water pollution is serious, leading to eutrophication. As people’s awareness of environmental protection, environment-friendly surface treatment technology gradually by people of all ages, in which the metal surface treatment due to the silane reagent used synthetic simple, environmentally friendly and to become one of the hot new technology research.Silane as a main component for the passivation film prepared in this thesis methyl triethoxysilane (silane alcohol) and y-aminopropyl triethoxysilane (a water-based silane) of two different metal surface treatment agents, chemical dipping manner steel substrate. Experiment to determine the best formulation according to two orthogonal experiment silane solution. Electrochemical Tafel polarization curves for silane films prepared to detect corrosion resistance, determine the two silane film curing temperature and curing time. Using copper sulfate drip method, electrochemical polarization curves and salt spray test for corrosion resistance of each single silane films were evaluated. The results showed that: in a short time, two silane film on the steel substrate has a better protective effect, and the effect of alcohol silane film is stronger than water-based silane film. But with time, the corrosion resistance of a single silane film sharply lower, less than the long-term protective effect. Use of elliptical polarization analyzer measured the thickness of the film thickness of each silane, video contact angle measuring the contact angle of silane films, scanning electron microscopy to characterize the surface morphology of the silane film. The results showed that: two silane can be more complete carbon film formed on the surface, but the thickness of the smaller, and uniform and dense films are poor.The test results found that a single silane film on steel will not achieve long-term protective effect from corrosion characteristics found they have complementary strengths and weaknesses, so both will be complex, so that the formation of a more uniform and dense composite silane film. γ-APS/MTES silane composite membrane resistance after CUSO4bit of time to126min, relatively homogeneous in terms of time silane films increased100min, METS/y-APS silane film is only10min, and a single silane film considerable time, corrosion resistance is not improved. The same salt spray test results obtained. SEM images found by the flatness of the composite film y-APS/MTES, uniformity and compactness are improved, combined with the thickness of the salt spray chart data and complex formation mechanism speculated silane films: MTES first filled in γ-APS silane film and then the film from the surface cross-linking reaction occurs deposited on its surface.The above advantages of complex thought and rare earth salts based on the experimental study began with a silane compound of cerium salt. Passivation process optimum parameters obtained through orthogonal experiment: Ce(NO3)330g/L, H2O230ml/L, pH value of2, the curing temperature140C°, curing time120min. Experimental results show that copper sulfate point cerium passive film on the steel can also play a protective role in anti-red time up to44min. After passivation film better corrosion resistance of silane is closed, the corrosion time Ce/y-APS passivation film up168min, Ce/MTES red longer passive film resistance, up to345min. From the salt spray and SEM micro-macro diagram in Figure speculated silane composite membrane formation mechanism: silane filling in voids and cracks first cerium passivation film, and then the membrane surface cross-linking reaction itself occurs deposited on the surface of the membrane. |
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