Preparation Of Silicate Waterborne Inorganic Zinc-rich Anticorrosion Coatings And Studies On Its Performance

Compared with organic coatings, waterborne inorganic zinc-rich coatings have beenwidely used in architrctural anticorrosion and industrial due to their long-term corrosionresisrance, high hardness, excellent adhesive force, favourable weather resistance, solventresistance and strong self-repairability. The coatings are mainly with water as solvent anddispersant, without releasing VOC and have low price, are currently become the mostdevelopment potential and high environment friendly coatings. However, they also exhibitsome disadvantages to greatly limit their applications including poor film-forming property,mechanical behavior are generally poor and bad storage stability. To solve the aboveproblems, the author added silicone-acrylic emulsion to the system, with the aid of organicpaint enhanced the flexibility and compactness of the coatings, which greatly improved thecorrosion resisrance and mechanical property of the coatings.In this paper, we have got a stable organic-inorganic latex modified potassium silicatesolution with high SiO2/K2O molar ratio was prepared by mixing silica sol with potassiumhydroxide modified by silicone-acrylic emulsion, and then the waterborne zinc-richcoating was obtained by the modified potassium silicate solution mixing flake zinc powderwith the mass ratio of3:1. Infrared test results showed that in the modified base material,the organic groups had been connected with the inorganic silicate skeleton.The storagestability of potassium silicate solution with high SiO2/K2O molar ratio exceed30days at5.5SiO2/K2O mole ratio,20%solid content and14.5%silicone-acrylic emulsion content.The waterborne zinc-rich coating prepared from modified high SiO2/K2O molar ratiopotassium silicate solutions could provide compact film and excellent performance ofhardness, adhesion, flexibility and corrosion resistance.In addition, the preparation of coating corrosion resistance and mechanical propertiesare more excellent than globular zinc powder for using flake zinc powder. The coatingimmersed in3.5%NaCl solution after595h, the Ecorr of flake coating was-0.560Vcompared with globular unmodified coating-0.915V. After immersed in0.3%HNO3 solution about72h, the corrosion weightless of flake coating was0.033g decreased by52%than that of globular unmodified0.050g. The amount of flake zinc powder was only1/6ofthe globular zinc powder, could reach the performance of globular zinc coating, andflexible performance raised a level. Using SEM and EDS tests for waterborne zinc-richcoatings, the flake coating surface was mutal crisscross superposition state, the coatinglayer porosity of flake coating has reduced than globular coating. EDS test results showedthat Si-O played a role by bonding, the content of Fe in the modified coating aftercorrosion had reduced, so that the coating has stronger corrosion resistance.