| Steel is a relatively wide range of metal materials in our life,the corrosion of steel in the air has caused a heavy loss.The protective film of the surface of the steel sheet is commonly used to prevent the corrosion of steel in the atmosphere.Hot dip galvanized steel plate is used in automobile,home appliances and other areas of life.But hot dip galvanized steel was easily to be corroded due to white products or changing color on the surface,which also could affect the service life and beauty of the steel.Most of the hot-dip galvanized steel sheet are treated by the last passivation process,However,with the gradual increase in people's living quality and environmental awareness,a kind of efficient and environment-friendly passivation technology without adding chromium is becoming more and more important due to the present passivation system contains highly toxic and carcinogenic of Cr(VI).In this paper,inorganic/organic composite passvating treatment was developed on the zinc galvanized steel,which is inorganic/organic composite passvating film and films of adding corrosion inhibitor were preliminarily studied by the neutral salt spray test and electrochemical tests,to established inorganic/organic composite passivating films of adding corrodion inhibitor system as the main research system.The Anshan Iron and steel production of hot dip galvanized steel sheet was chosen as the substrate of zinc,the corrosion resistance of composite passivation coating is tested by by neutral salt spray test and electrochemical detection was preliminary studied.The system adding corrosion inhibitor of organic/inorganic composite passivation system was chosen as the main research object and was researched in detail.The optimal composition of each component is shown as follows through orthogonal experiment results:KH-560:3.5 g,H2TiF6:0.9 g,NH4VO3:0.09 g,resin:20 g,sealing agent:0.20 g,K-12:0.05 g,1788:0.15 g and AEO-7:0.20 g.Optimum process parameters are obtained through the single factor experiment:passivation solution pH of 5.0,curing temperature of 150 DEG C,curing time for 60 seconds.The thickness of the films was 0.5-0.8 g/m2,and the performance of the optimum compound passivation solution was tested.Based on the experimental research and industrial production performance testing methods,the passivating film properties were tested.It was shown that the composite passivating film is a dual-layer corrosion controlling process in SST orthogonal test whose white rust is less than 5%after 96 h with good heat resistance of 240 ?,and film adhesion reached level 1?2.The surface morphology of the passive film was observed and detected by Scanning Electron Microscope(SEM).The detection results show that there is no micro crack on the surface of the passivation film before salt spray corrosion,and it is a uniform and dense protective film.The thickness of the membrane ranges from micron to nanometer,about 1?1.5?m in the section.In the process of the experiment,the microstructure and phase of the passive film were detected by using the Fu Liye transform infrared spectrometer(ATR-FTIR)and X-ray photoelectron spectroscopy(XPS).The result showed that the films consisted mainly of organic functional groups including-(CH2)n-,-OH,N-H,C=O,C-Si,C-O-C,C-N,Si-O-Si,Si-O-C and other organic functional groups.Through the analysis of passivation film and corrosion products by SEM,XRD and EDS,corrosion products are mainly consisted of compounds of Zn,C,O,Cl,P including organic of Zn,Zn(OH)2,Zn5(OH)8Cl2·H2O,ect.In a word,it can be concluded that the passivation agent formed on the surface of galvanized passive film changed the hot dip galvanized substrate surface morphology and the passivation film can effectively prevent penetration of corrosive medium to the substrate,to protect the hot dip galvanized matrix from corroding,improve the corrosion resistance of the zinc matrix,and nearly reached industrial application requirement standard. |
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