Prepared And Anti-Corrosion Performance Of Inorganic-Organic Composite Passivation Solution On Galvanized Wide Strip

In this thesis, a series of chromium-free passivating products were designed in view of the fact that the galvanized wide strip surface hexavalent chromium passivation has pollution to the environment. The designed products accord with the demands of both the restrictions on the use of certain hazardous substances in electrical and electronic equipment directive(hereinafter referred to as "RoHS directive") and the waste electrical and electronic equipment directive(hereinafter referred to as "the WEEE directive"), which were published in the official gazette by European Commission. The organic silane and inorganic corrosion inhibitor were well combined by adjusting the amount of each material and the reaction ratio to prepare the environmental benefit and passivating products, which are applicable for industrial production. The work mainly contain three parts:(1) According to the principle of organic silane may hydrolyze under acidic condition, the gamma-(2,3-epoxypropyl oxygen) dimethoxy silane(KH560) and N-(beta aminoethyl)-gamma-ammonia propyl methyl dimethoxy silane(KH602) were treated to undergo the hydrolysis reaction, then a certain amount of inorganic inhibitor Na3VO4 and TiOSO4 were added, the mixture was well stirred, dispersed and mixed to obtain the chromium-free passivating products in pilot test scale. The passivation film was tested by simulating industrial coating film forming technology. The film had a good electrochemical performance and only 4%~6% white rust area was observed on 72 h salt spray test, the corrosion resistance could be compared to the chromate passivation film. Moreover, adhesion experiment and scanning electron microscope(SEM) analysis results showed that the adhesion of the passivation film had reached grade 1 and the surface structure was uniform and dense.(2) In view of the analysis solutions of the fingerprint resistant passivation products, sodium molybdate was dissolved in the water, after using organic acid to adjust pH to neutral and adding a certain amount of modified nano-SiO2 to the solution, the inorganic passivation solution was prepared; silane coupling agent gamma-propyl methyl acryloyl oxygen silane(KH570) and double top oxygen radicals [gamma(triethoxy silicon) propyl]-tetrasulfide(KH858) were compounded to get the organic silane passivation solution; and then the two kinds of passivation solution were further compounded to prepare the organic silane molybdate passivation solution, and then its film properties were characterized.(3) The use of the foreign related products was studied in Meishan Iron & Steel Co., Ltd., baosteel by systematically analyzing the physical and chemical properties of the chromium-free passivating products and speculating the film-forming mechanism, which may supply theoretical and technical support for development of chromium-free passivating products and further industrialization. In this subject, the composite chromium-free passivation solution in pilot test scale has been successfully prepared and used for surface treatment of galvanized sheet. The passivation solution used demineralized water as solvent and contained no hexavalent chromium, meeting with the RoHS directive and WEEE directive requirements; in addition, it had simple coating process, low cost, stable performance, good industrial use and popularization value.