Preparation And Anticorrosion Application Of Squamous Zn-Al Based Alloy

The flake-like Zn-Al-Mg-Ce alloy powder was prepared by wet ball milling.The powder was characterized by SEM,specific surface area(BET),particle size analysis etc.The effects of ball milling medium gradation,ball milling time,ball milling speed,and ball milling additives on the morphology,average particle size,specific surface area,and water surface coverage of flake-like Zn-Al-Mg-Ce alloy powder were studied.In order to investigate the effect of components of alloy on its anticorrosive performances,other multi-component flake Zn-Al alloy powders were also prepared at optimal conditions and used in the preparation of chromium-free zinc aluminum coating.The waterborne epoxy Zn-Al base anticorrosive coating were prepared using Zn-Al base alloy powders as pigments,the waterborne epoxy resin emulsion as the main film-forming material.The effects of various components of coating on their properties were studied.The best formula of the coating was determined by determination of adhesion,hardness,water resistance,salt spray resistance and Tafel curve.the flake-like Zn-Al-Mg-Ce alloy powder was prepared by wet ball milling,in the process,304 stainless steel ball was used as ball milling medium,anhydrous ethanol was used as solvent,and the ratio of ball to material was 10 :1,and three different gradations of milling ball with various diameters were adopted.The best conditions for ball milling process is described as follows: the ball milling gradation is C group,the ball milling time is 9h,the ball mill speed is 500 r / min,the best grinding additives are PEG-1000 and triethanolamine.The flake Zn-Al-Mg-Ce alloy powder prepared by the optimal ball milling process exhibits high flake degree,bright color and clean surface.The water surface coverage of the alloy powder is 3545 cm2 / g,the average particle size is about 12 ?m,the specific surface area is 2221.3 cm2 / g,and the diameter-thickness ratio is about 30.The particle size and flake degree of the product meet requirements of flake alloy powder for chromium-free zinc-aluminum coatings well.Three kinds of flake zinc-aluminum alloy powders,including flake-like Zn-Al-Mg-Ce,Zn-Al-Mg,Zn-Al alloy powders were prepared with spherical alloy powder under optimal conditions,and then were used in anticorrosive dacromet coating.The neutral salt spray test and Tafel curve were used to test the corrosion resistance of the coating.The results show that flake Zn-Al-Mg-Ce alloy powder exhibits the best anticorrosive performance,and the neutral salt spray test time of decromet coating is730 hrs,corrosive current of this coating is only 0.102 percent of that for its metal substrate,which indicate that that the addition of Mg and Ce demonstrate significant improvement on the corrosion resistance of coating.The optimum formulation of waterborne epoxy anticorrosive coating was studied.The effects of volume pigment concentration(PVC),different anticorrosive pigments,and dosage of KH560 and dispersant on the properties of the coating were investigated by water resistance,netral salt spray test resistance,adhesion test and Tafel curve test.The best coating formulation was determined as follows: flake Zn-Al-Mg-Ce alloy powder as anticorrosive pigment,PVC 28 %,KH560 dosage 3.2 % ?6.4 %,dispersant dosage 1 %?1.5 %,defoamer and leveling agent dosage 1.3 %,and film forming additive 3 %.