| In order to clean up the metal surface attached to the foreign matter(dust,rust,oil,etc.),to obtain a good surface of the metal matrix to meet the coating requirements,to ensure that the coating film and the substrate have a better bond and anti-corrosion properties,the metal substrate needs to be surface pretreatment before painting.Traditional metal surface pretreatment is mainly phosphate phosphating and chromate passivation process,both of which have good anti-corrosion effect,but can cause different degrees of environmental hazards,phosphating is easy to produce a large amount of phosphate waste solution,chromate treatment after the residual hexavalent chromium ions are carcinogenic.It is found that the silane conversion film obtained by silane hydrolysis solution for metal surface treatment has better anti-corrosion effect and is environmentally friendly and reliable,which can significantly improve the bonding strength of organic coating and metal substrate,thus better solving the problem of losing protection of the substrate due to coating peeling.As a new metal surface treatment process,with the continuous development of silane pretreatment technology,it is expected to replace traditional metal surface pretreatment processes such as phosphating and chromate passivation in the near future.Based on this research,the effect of zinc aluminum powder mass ratio on the corrosion resistance of fluorocarbon zinc aluminum coating was investigated,and the appearance and composition of the coating were observed and analyzed.The immersion experiments and electrochemical tests were conducted on the fluorocarbon zinc aluminum coatings prepared with different zinc aluminum powder mass ratios,and it was found that when the zinc aluminum powder mass ratio was 7:3,the fluorocarbon zinc aluminum coating could be immersed in 3.5wt.%Na Cl solution for a maximum of 28 days,with a minimum corrosion current density of 8.43×10-7and better corrosion resistance.Therefore,a fluorocarbon zinc aluminum coating was prepared,and the viscosity of the fluorocarbon zinc aluminum coating prepared with a zinc aluminum powder mass ratio of 7:3 was tested to be 27s,and the p H value was 6.5.After the film was cured at room temperature,the adhesion grade of the coating was measured to be 7,the hardness was 4H,and the thickness was 12-20?m.In this project,we chose methyltrimethoxysilane(MTMS)to prepare silane hydrolysis solution to pretreat the substrate,and designed a four-factor,three-level experiment on the effect of silane hydrolysis process conditions on the performance of fluorocarbon zinc aluminum coating,and counted the corrosion resistance and adhesion of silane conversion film-fluorocarbon zinc aluminum coating under different silane hydrolysis process conditions,firstly considering the corrosion resistance,followed by the adhesion between the coating and the substrate,and analyzed the optimal In order to compare the fluorocarbon zinc aluminum coating with and without silane MTMS pretreatment,the surface microstructure and morphology,the composition of the coating before and after corrosion were analyzed by SEM and EDS.The corrosion resistance of the coating was compared by brine immersion test,dynamic potential polarization curve and AC impedance test,and it was concluded that the corrosion resistance of the fluorocarbon zinc aluminum coating with silane MTMS pretreatment could be significantly improved and the service life of the fluorocarbon zinc aluminum coating could be extended.Finally,the effects of the addition of sodium phosphomolybdate and nano-Si O2sol on the performance of the fluorocarbon zinc aluminum coating were studied through the dynamic potential polarization curve and brine immersion experiments,and the results showed that sodium phosphomolybdate could improve the anti-corrosion effect of the fluorocarbon zinc aluminum coating,and the corrosion resistance of the prepared fluorocarbon zinc aluminum coating was better when the addition of sodium phosphomolybdate was 1.2 wt.%,and the immersion failure in 3.5wt.%Na Cl solution was38 days.The nano Si O2sol can improve the anti-corrosion effect of fluorocarbon zinc aluminum coating,when the nano Si O2sol is added at 3wt.%,the prepared fluorocarbon zinc aluminum coating has better corrosion resistance,and the failure days of immersion in3.5wt.%Na Cl solution is 39 days,which can achieve the silane MTMS conversion film to improve the anti-corrosion effect of fluorocarbon zinc aluminum coating,and the hardness is increased to 5H. |
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