Research On Hot Dip Galvanized Plate Of Organic-Inorganic Composite Passivation And Its Properties

With the development of the economy, hot dip galvanized steel sheet is vigorous in in the car, household appliances, plumbing and other industries, market demand is becoming more and more big. However, hot galvanized steel sheet is easy to corrosion rusty black in the moist environment, it affects the service life and beautiful. In order to improve the corrosion resistance of galvanized steel, usually people treat passivation on the surface. In the past people often used chromate passivation process. With the toxic of chromate and the enhancement of people’s environmental protection consciousness, to find an effective substitute chromate passivation technology of new is imminent.The paper studied the three passivation technology of galvanized steel in this paper: passivation technology basic acrylic resin, acid passivation technology of acrylic resin and silane passivation technology-inorganic compound. Though salt spray test and electrochemical test and evaluate three kinds of process. At last, a further research should be choosed the silane passivation technology-inorganic compound.To use orthogonal experiment of silane and inorganic composite components to optimize passivated technology experiment, and get the best composition. On the basic of it, improved experimental formula of the silane and optimize passivation process (passivator pH and curing temperature) by using the orthogonal experiment and single-factor experiment of acidic acrylic resin. The final passivation and formula:the silane KH550is2g, ammonium fluosilicate is4g, oxygen titanium sulfate is0.4g,0.25g of ammonium dihydrogen phosphate, acetylacetone oxygen vanadium is0.15g,0.2g protective colloid is0.2g,0.1g of emulsifier, dispersant is0.2g and acrylic resin is14g. To apply optimized formula to reformulate passivator, then passivate film,white rust area is less than5%after72hours salt spray test, and reach the anticipate.Combined with experimental research and test method of industrial production performance, To use the optimized acrylic resin-silane-inorganic compound passivation formula and preparation process of passivation film to test function. Test results show that the composite passivating film has excellent corrosion resistance, heat resistant performance and the coating performance (grade1-2).As is shown in fourier transform infrared spectroscopy about Resin-Silane-inorganic composite passivation film, passivation film mainly contains carbon chaini-COOH、-NH2、 Si-O-Si、Si-O-Zn-(CH2)n-,etc. The existence of Si-O-Zn indicates that silane has combined with the base by chemical bond, which makes the film and the substrate binding force enhancement. The existence of Si-O-Si indicates that the condensation reaction between the silanol films is formed.For film full and narrow scan of spectroscopy passivation about surface elements using X-ray photoelectron, the result of fitting shows the passivation film has formed chemical bond of C-O-Si、Si-O-Si、O-Zn, ect, which consists with the results of infrared spectroscopy. The existence of C-O-Si and Si-O-Si indicates that ondensation reaction happens mutually between acrylic resin and the silanol and dense passivation film is formed in the surface of film.Through SEM, salt spray test, electrochemical detection, infrared spectroscopy, X-ray photoelectron, the results show that passivating film is formed on the surface of hot dip galvanizing, which changes the morphology of base. Dense layer of silane and acrylic resin can effectively prevent penetration of corrosive media to the substrate.It can protect the substrate, which improves the corrosion resisitence of base.Through the analysis of passive film and corrosion products by SEM、XRD and EDS, corrosion products are mainly compounds of Zn、C、O、H、Cl、P、S, including organics of ZnO、Zn(OH)2、Zn5(OH)8Cl2·H2O and C13, ect.