| Zinc powder and aluminum powder are widely used in traditional solvent-based coatings due to their superior metallic properties.Nowadays,with the promotion of people's concept of environmental protection,green water-based coatings gradually get people's attention,and an emerging and really environmentally friendly water-based chrome-free Dacromet preparation technology is gradually becoming the focus of research.Flake zinc powder and aluminum powder are the main components of waterborne chrome-free Dacroix coatings,and their properties directly affect the properties of the coatings.But when aluminum powder is used in waterborne coating,it is easy to be corroded and release a lot of hydrogen,which causes inconvenience to production and storage,and also weakens the metallic luster of aluminum powder.In addition,the activity of zinc powder in waterborne coatings is too strong,but the corrosion resistance,dispersion and subsidence resistance are poor,which will easily lead to coating failure,thus limiting the application of zinc powder aluminum powder.Therefore,it is an urgent problem to improve the corrosion resistance and dispersion performance of zinc powder and aluminum powder to make it suitable for waterborne coatings.For zinc powder,through previous literature review and experimental exploration,firstly,this article adopts the single factor experiments to analyze the effect of various factors on the erosion resistance and surface morphology of modified zinc powder,using silane coupling agent KH570 as modifier,corrosion resistance,resistance to settlement of samples as evaluation index,through the four factors three levels orthogonal experiment optimization to get the optimal process conditions:zinc powder 5 g,KH570 dosage of 6%,water/alcohol=1:4,pH=4,reaction at 35? for 3 h.In this case,the surface of the flake zinc powder was coated with a dense silane film,and the corrosion resistance was greatly improved.The volume of hydrogen evolution in hydrochloric acid solution with pH=1 for half a month was only 0.2 mL,and the protective factor was as high as 99.5%.However,the surface hydrophobicity of zinc powder modified by KH570 is increased,and the dispersion of zinc powder in aqueous solvent is poor.So in this paper,on the surface of KH570/zinc powder to introduce acrylic monomers containing hydrophilic groups,and explore the dosage of monomer,initiator,reaction time on the influence of zinc powder surface morphology and corrosion resistance,thus draw the optimization process:the acrylic monomers in the quality of zinc powder 30%,the dosage of initiator AIBN 3%of dosage of monomer,the reaction time of 5 h,the reaction temperature at 70?.Under the condition of optimized preparation of acrylic/KH570/zinc,through SEM,EDS and FTIR,XRD,and the analysis of the corrosion resistance,dispersion test and so on characterization results show that the modified surface of zinc powder coated with a layer of amorphous dense protective film,soaking in the pH=1 sample of the hydrochloric acid in the solution after half month,almost no hydrogen precipitation in room temperature,protect factor as high as 99.6%,corrosion resistance is superior.The surface of zinc powder is changed from hydrophobic to hydrophilic,and can be evenly dispersed in water,thus realizing its hydrophilic surface,which lays a foundation for its application in water-based coatings.For aluminium powder,at first,ethyl orthosilicate(TEOS)as precursor,and a protective layer of SiO2 was coated on the surface of aluminum powder through the traditional sol/gel process.Based on the evaluation criteria of hydrogen evolution volume and glossiness,the orthogonal experiment L16(45)was used to analyze and optimize the following results:the mass of aluminum is 5 g,reaction temperature is 40?,reaction time is 4 h,TEOS is 7 g,H2O is 16 g and ammonia water is 5 g.It is concluded that the molar ratio of Al/TEOS is 5.52,the molar ratio of H2O/TEOS is 26.5,and the ammonia concentration of the catalyst is controlled to account for about 0.05 of the total volume of the system.Under these conditions,SiO2 coated the surface of aluminum powder with a dense non-static SiO2 coating layer,but the luster of aluminum powder decreased by 22.8%.In order to maintain the gloss of aluminum powder and combine the advantages of SiO2 coating aluminum powder,an organic/inorganic coating layer was applied on the surface of aluminum powder by modified sol/gel method,in which TEOS and VTPS(Vinyl triisopropoxysilane)were used as precursors.By studying the effects of TEOS/VTPS ratio,reaction temperature,reaction time,catalyst dosage and water dosage on the corrosion resistance of aluminum powder,it is concluded that when TEOS/VTPS=3:4,catalyst ammonia dosage of 5 g,water dosage of 16 g,reaction time of 6 h,reaction temperature of 30?,the obtained TV/Al has good corrosion resistance and basically maintains its gloss.Next,in order to further improve the dispersivity of the aluminum powder in water,this article on the basis of TEOS/VTPS coated aluminium power,introduced on the surface of methyl methacrylate(MMA)and acrylic acid(AA),through the polymerization of MMA and AA and VTPS surface double bond,and get the denser TVMA/Al cladding layer,and analyzed the TVMA/Al surface morphology,structure,corrosion resistance and dispersion in water,finally got good corrosion resistance and dispersion in water good aluminum powder. |
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