Influence Of Modified Zinc Powder On Preparation Of Waterborne Silicate Zinc-rich Anticorrosion Coatingsp

Water-based zinc-rich anti-corrosion coatings have excellent corrosion resistance,physical properties and passivation,and are widely used in large-scale construction steel fields such as industry and marine.Flake zinc powder has gradually become the best pigment in the preparation of zinc-rich coatings due to its advantages in anti-corrosion.However,the problems of poor dispersibility and short anticorrosion period of flake zinc powder affect the performance of the coating and reduce the use effect of zinc powder in coatings.In view of the above problems,this paper uses silane coupling agent compound phosphate to modify flake zinc powder,and test the anticorrosion effect of flake zinc powder after modification;The zinc powder was prepared into a water-based silicate zinc-rich anti-corrosion coating,and the effect of zinc powder modification on the coating performance was studied.The results show that:(1)The best conditions for obtaining modified zinc flakes are obtained by using phosphoric acid modified zinc flakes,KH570 modified zinc flakes and KH570/phosphoric acid composite modified zinc flakes separately: first immerse the zinc flakes in a volume fraction of 3 % phosphoric acid modification solution,and then immersed in a 5% silane coupling agent KH570 modification solution for a modification time of 35 min.The flaky zinc powder was modified by the optimal modification conditions.Through energy spectrum analysis,sedimentation volume,activation degree test and SEM analysis,it was found that there was a layer of silanol group and phosphate compound on the surface of the composite modified flaky zinc powder.For the hybrid film,the maximum sedimentation volume is only 0.6ml/g,the surface of the composite modified zinc powder is relatively rough,and there are striplike dense substances.(2)The modified zinc powder was prepared into a zinc-rich coating,and the analysis of polarization curves,electrochemical impedance spectroscopy and corrosion topography showed that the corrosion potential of the composite modified coating was-0.82 V,which was higher than that of the unmodified coating.The zinc powder coating is increased by 16%,and the surface of the composite modified zinc powder coating has less signs of corrosion,indicating that the composite modified zinc powder coating has the strongest corrosion resistance.(3)In order to further improve the modification effect,KH570-BTSE silane coupling agent was used to compound phytic acid to modify flake zinc powder.Bisilane/phytic acid composite modification solution formula:dual silane coupling agent(5% by volume),phytic acid(1.2% by volume),silica sol(concentration 4g/L),in a water bath at 35°C Hydrolyzed,adjusted the p H to 9,and the modified immersion time of zinc powder was35 minutes.Through energy spectrum analysis,sedimentation volume,activation degree test and SEM analysis,it is found that there is a hybrid film formed by polycondensation of phytic acid and silyl hydroxyl groups of bisilane on the surface of bissilane composite phytic acid modified zinc powder,and the maximum sedimentation volume is only 0.57 ml /g,the activation degree of the composite modified zinc powder reached 55.99%,and the surface of the composite modified flake zinc powder and the surrounding micelle particles were smooth and dense.(4)The self-corrosion potential of the bissilane composite phytic acid modified zinc powder coating is increased by 0.155 V compared with that of the unmodified coating,and the self-corrosion current density is reduced by an order of magnitude,indicating that the bissilane composite phytic acid modified coating The effective time in corrosive medium is longer than that of monosilane composite phosphoric acid modified coating.The results of mechanism analysis show that the silane coupling agent forms molecular chains with organic functional groups at both ends through dehydration and condensation.The phosphate ions generated by hydrolysis can react with zinc particles to form phosphates,and the free phosphorus hydroxyl groups can also react with silane solution.The silyl hydroxyl groups in the compound form mutually cross-linked hydroxyl groups,and the silane molecules can also form bonds on the surface of the zinc particles,and the composite protective film formed by cross-linking can effectively improve the corrosion resistance of the zinc powder.