Modification Study Of Inorganic Silicate Zinc-rich Coatings

Inorganic silicate zinc-rich coatings are widely used in the field of corrosion prevention because of their good corrosion resistance,long corrosion life and zero VOC emission.The performance of inorganic silicate zinc-rich coatings is mainly determined by their filler zinc powder.Compared to the most common spherical zinc powder,zinc flake has better physical shielding properties and provides better protection to the substrate with the same amount of addition.However,without any treatment of zinc flakes,the high surface energy of zinc flakes is difficult to disperse sufficiently in the base material,which significantly limits its use in zinc-rich coatings.Therefore,it is a new research direction to overcome the problems of agglomeration and sedimentation of zinc flake powder,and further research is needed for the filling of pore structure generated by zinc powder.To address the above issues,this paper investigates the modification of scale-like zinc powder and the effect of 2D nanosheets with double electric layer which based on hydrotalcite laminates on the corrosion resistance of coatings,respectively.The main research content of the paper:1.Modification study on zinc powder.The zinc powder was modified with silane coupling agent KH560,and the optimum conditions for modification were determined by single factor analysis:the zinc powder was modified for 60 minutes at 70℃in a modification solution with p H=9,where the modification solution was an alcoholic aqueous solution of KH560,and the content of KH560 was 8%of the mass of zinc powder.The modified zinc powder was made into coatings and the overall performance was evaluated,and the optimum addition amount of zinc powder was determined to be 40%of the mass of the base material.After the salt spray and electrochemical tests,it was discovered that the corrosion resistance of the modified coating was obviously superior to that of the unmodified coating,indicating that the modification of zinc powder could really enhance the corrosion resistance of the aqueous silicate coating.2.Study on the preparation of 2D nanosheets with double electric layer.Hydrotalcite with high charge density was prepared under the condition of Mg/Al=2 and reaction p H of 9.5,and the two-dimensional nanosheets with two-electron layers carrying different anions were prepared using it as a substrate.The prepared materials were added to coatings to make coatings and tested for salt spray resistance,and it was found that the coatings with the addition of 6%of 2D nanosheets with double electric layer which carrying SO₄^2-had the best corrosion resistance.Meanwhile,electrochemical tests were conducted on the coating with layered double hydroxides,the coating with 2D nanosheets that have double electric layer and the blank coating,respectively.The results showed that after 25 days of immersion in 3.5%Na Cl,the coating with the addition of the double electron layer material had the smallest corrosion current of 4.53×10^-5m A,and its self-corrosion potential was positively shifted the most,from-0.75 V to-0.66 V,this indicating that the prepared double layer material can further enhance the corrosion resistance of the coating.