Synthesis of silica coated zinc powder by sol-gel processes

Silica-coated zinc powders from the ultra fine zinc powder were manufactured by a sot-gel method. The reaction was carried out by controlling various process parameters such as the amount of NH3 and NaCl, the reaction time and the number of coating process. The silica- coated zinc powders were identified by a variety of characterization techniques such as SEM-EDX, TEM, PSA and ELS analysis. It was found that the thickness of silica coating layer and particle size could be controlled by the reaction time and the number of coating process. The particle size decreases with the decrement of molar ratio of NH3 and the increment of concentration. The dispersability of silica-coated zinc powders have improved nearly four times than that of raw zinc powders and their resistance to acid also improved. The silica-coated zinc powder would be used as a pigment for anti-corrosive coatings with high durability.