| The preparation of polymer rod grinding additives and the technique for preparing flake zinc-aluminum alloy by rod grinding were systematically studied.The flake zinc-aluminum alloy was applied in chromium-free Dacromet coating solution.The composition and manufacturing process of the coating solution were explored,and the optimized formulation of the coating was obtained.The main results are as follows:1.Two kinds of rod grinding additives,polymer F and H were prepared,the concentration of monomers,the amount of initiator and the amount of chain transfer agent used in the preparation were studied.Under this experimental condition,the suitable synthetic conditions for polymer used as grinding additives were as follows:the concentration of monomers was 5%~10%,the amount of chain initiator was 0.25~0.5%,and the amount of chain transfer agent was 6~8%.2.Flake zinc aluminum alloy was prepared by wet rod-milling using spherical zinc-aluminum alloy powder as raw material.The particle size distribution,morphology,specific surface area and water surface covering of the prepared flake zinc aluminum alloy were characterized by laser particle size analyzer,scanning electron microscope(SEM),specific surface analyzer and cryptometer.The influences of process parameters such as milling gradation,rod-milling time,rotating speed,and the kind of additives on the rod-milling process were investigated.The results show that the desired results can be achieved by adopting a greater proportion of grinding rods with larger diameter,relatively faster rotating speed(150~200 r/min)and moderate milling time(12~20h)when stearic acid is used as rod-milling additive.According to the orthogonal test,the influencing order of impact factors on the water surface coverage ratio of the product is:rod-milling time>rotation speed>rod-milling gradation>additives.The optimum level combination is as follow:polymer F is used as the additive,the gradation of rod-milling is B,the speed of rod-milling is 150 r/min,and the time of rod-milling is16h.Under these conditions,the product with good shape and high brightness can be prepared,its average particle size,specific surface area and the water surface coverage ratio of product are12.83?m,2402.3 cm~2/g and 3856cm~2/g,respecitvely.3.For the preparation of chromium-free Dacromet coatings,the effects of different emulsifiers,sintering times,temperatures and passivators on the adhesive force and anti-corrosive performance of coating were investigated.It was concluded that obtained coatings exhibit the best appearance and the greatest adhesive force using OP-10 was as emulsifier,sodium phosphomolybdate as passivator,and sintered for 30 minutes at300?.The coating showed the adhesive force of level 0 with silver-grey metallic luster.The salt-spray test shows that the corrosion resistance of the coating is the strongest under this condition. |
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