Preparation And Properties Research On Waterborne Inorganic Modified High Modulus Potassium Silicate Zinc-rich Coatings

The waterborne inorganic silicate zinc-rich coatings have two-component anticorrosive properties prepared by using an aqueous solution of silicate as a base material,metallic zinc powder as a pigment,and adding some coating additives.The coating uses water as solvent and diluent,the cost is low,production process has no pollution to the environment,construction is convenient,and has excellent corrosion resistance and solvent resistance.Widely used in the field of anti-corrosion engineering,but there are some defects such as brittle and poor mechanical properties.Therefore,the experiment uses silica sol,potassium hydroxide,and deionized water as raw materials,and modified by silicon-acrylic emulsion to prepare a stable modified high modulus potassium silicate solution,and mixes zinc powder,zinc and aluminum,to make waterborne inorganic modified high modulus potassium silicate zinc-rich coatings.In this thesis,the preparation technology of modified high modulus potassium silicate solution,the quality ratio of zinc powder to modified base material,the content of flake aluminum powder and the effect of arc spraying bottom layer on the properties of water-borne inorganic modified high modulus potassium silicate zinc-rich coatings were studied.The silicate solution is the key to the film formation of the coating.The selection of the silicate type,modulus and temperature,time of preparation,and the amount of the silicone-acrylic emulsion have a certain influence on the preparation of the high modulus silicate solution.In this paper,the characteristics of three alkali metal silicates,lithium silicate,sodium silicate and potassium silicate were compared and analyzed,and the potassium silicate solution was finally used as the film-forming base material.The effects of modulus,temperature and stirring time on the storage stability,solution state and coating properties of high modulus potassium silicate solution were studied by single factor experiment.The silicone-acrylic emulsion BF-400 was used to modify the base material.The intermetallic particle size distribution of silica colloid in potassium silicate solution with modulus 5.5,6.0,6.5 was analyzed by nano laser particle size analyzer,and the optimum preparation conditions of the modified base material was obtained.The potassium silicate modulus was 6.5,the temperature was 50°C,the stirring time was 15 min,and the silicone-acrylic emulsion content was 20 wt.%.The effect of different zinc powder content on the properties of coatings was studied,and the coatings with a mass ratio of zinc powder to modified base material of 2:1,2.5:1 and 3:1 were prepared.The microstructure and film forming of the coatings was compared and analyzed by scanning electron microscopy(SEM),energy spectrum analysis(EDS),X-ray diffraction analysis(XRD),the corrosion properties were used by potentiodynamic polarization curve test and electrochemical impedance spectroscopy(EIS).The results show that when the mass ratio of zinc powder to modified base material is 2.5:1,the prepared coating has better film forming property,more dense,better adhesion and corrosion resistance.The immersion time can reach to 15 days in 3.5wt.% NaCl solution(pH=6).In addition,5wt.%,10 wt.%,15 wt.%,20 wt.% of flake aluminum powder were added to the spherical zinc powder to study the influence of the amount of aluminum powder added in the zinc-aluminum mixed powder on the coating properties.The results show that when the aluminum powder content accounts for 15 wt.% of zinc aluminum powder,the corrosion resistance of the prepared coating was better,and the immersion time can reach to 40 days in 3.5wt.% NaCl solution(pH=6).Finally,the composite research on waterborne inorganic modified high modulus potassium silicate zinc-rich coating and arc spraying was carried out,the substrate was sprayed with pure Zn,Zn-Al15(zinc-aluminum alloy wire,of which aluminum content accounted for 15 wt.%)and pure Al,as the bottom layer of zinc-rich coating.The composite and corrosion resistance of the arc sprayed primer layer and the zinc-rich coating were studied by scanning electron microscopy and electrochemical test.The experimental results show that the arc sprayed pure Al coating has good composite property with the zinc-rich coating,and the prepared composite coating can be immersed in 3.5wt.% NaCl solution(pH=6)for 71 days.