Preparation Technology Of Electric Double-Layer Waterborne Inorganic Zinc-Rich Coatings

Water-borne potassium silicate inorganic zinc-rich coatings had been becoming an advanced hotspot due to its self-setting at room temperature, excellent corrosion resistance, water resistance, price advantage. In order to ensure electrochemical protection of coatings, a high content of zinc powder is required. Due to high pigments volume concentration(PVC), it is hard for zinc powder to disperse uniformly in coatings. In addition, zinc powder itself has a relatively low surface area/weight ratio, which makes the coating exist serious defects. Then corrosion resistance of the coating reduces greatly.To solve the above problems, the author added electric double-layer powder based on montmorillonite to coatings. With the help of electrostatic interaction of electric double-layer structure, we prepared coating with characteristics of electric double layer. Because montmorillonite lamellas are with positive charge, they can directly reject positive and negative ions which can corrode substrate. Also compactness of the coating can greatly improve when add electric double-layer powder based on montmorillonite with fine particle and good dispersion into the coatings.In this paper, firstly mixing silica sol and potassium silicate solution, we prepared potassium silicate solution with high SiO2/K2O molar ratio. The author discussed effects on preparing potassium silicate solution of temperature, varieties and amounts of the organic siloxane. Infrared test results showed that compared with potassium silicate solution with low SiO2/K2O molar ratio, increase of the SiO2/K2O molar ratio did not change position of the characteristic absorption peaks and only peak intensity increased.Mixing potassium silicate solution, zinc powder and electric double-layer powder based on montmorillonite, we got the new-fashioned inorganic coatings. By SEM test and electrochemical performance test, we investigated performance of the coating. Scanning electron microscopy test results showed that montmorillonite lamellas were filled into the coatings and porosity of the coatings could reduce significantly. Also it could effectively prevent corrosion media to corroding substrate. Electrochemical impedance and polarization curve results showed that adding montmorillonite layers could greatly improve corrosion resistance of the coating. When the quality of montmorillonite layers reached 10%, impedance of coating decreased significantly and the corrosion current density increased by about one orders of magnitude.