Preparation And Modification Of Scale Zn-Al Alloy And Its Application In Waterborne Epoxy Zinc-rich Aluminum Coatings

In this paper,flake-like zinc-aluminum alloy powders were prepared by ball-milling,the size distribution,specific surface area,micro-morphology,element composition,crystal morphology and dispersion stability of flake-like zinc-aluminium powder were determined by particle size analyzer,BET,SEM,EDS,XRD and sedimentation height.The effects of technologic condition on their morphologies and the feature of products were thoroughly investigated.By using this kind of flake-like zinc-aluminum alloy powders as pigments and water-borne epoxy resin as film-forming material,waterborne epoxy zinc-rich aluminum coating was prepared.The effects of various factors on coating performance were studied by measuring the hardness,adhesion,acid resistance,alkali resistance and salt spray resistance of coatings,and the optimum composition of the coating solution was determined.On the exploration of ball-milling technology for flake-like zinc-aluminum alloy,the effects of ball-milling time,ball-milling speed,ball-milling additives,ball-milling solvents,solid-liquid ratio and other factors on the products are studied.The performance of products obtained under various factors were analyzed.The results show that the best grinding conditions were as follows:ball milling solvent is anhydrous ethanol as,solid-liquid ratio is 1:2,grinding material is 304 stainless steel ball,ball-to-material ratio is 12:1,ball milling speed is 600 r/min,ball milling time is 9 h,ball milling additives are diethanolamine-maleic anhydride copolymer and its complexes.Aiming at overcoming the shortcomings of flaky Zn-Al alloy in waterborne coatings,SiO₂ coated waterborne flaky Zn-Al powders were prepared by sol-gel method,and the properties of these obtained products under various conditions were tested.The results show that a uniform and compact SiO₂ film can be coated on the surface of flake-like zinc-aluminium pigments by using TEOS as silicon source,NH3.H2O as catalyst,n-butanol as reaction solvent under the ratio of m?TEOS?:m?ZA?powder of2.5:1.The average particle size of flake-like zinc-aluminum pigment powder coated with SiO₂ film is 12.29?m,and the acid resistance of the product improved significantly.Water-borne epoxy resins with good hydrophilicity were prepared by modification of solvent-based E-44 epoxy resin with diethanolamine.water-borne epoxy Zinc-rich aluminum coatings were formulated using it as film-forming material,the effect of PVC concentration,different Zinc-Aluminum powder,curing agent types,wetting dispersant,leveling agent,defoamer and silane coupling agent on the properties of these coatings were studied by testing the physical properties and anticorrosion properties of the coatings,hence evaluated the optimum conditions.The results show that water-borne epoxy zinc-rich aluminum coating with smooth appearance,good physical properties and corrosion resistance can be obtained by using SiO₂ coated flake zinc-aluminum as pigment powder,40%PVC concentration,DY-175 Waterborne Epoxy Curing Agent,1%²%,wetting dispersant,0.3%leveling agent,1 g silane coupling agent and0.2%⁰.3%defoamer.