Preparation And Performance Of Water-based Lubricated Coating For Galvanized Steel Sheet

Lubricated steel sheet is a kind of functional organic coated plate, which can directly be used or painted after press forming, instead of the use of anti-rust oil before coiling and the use of pressing oil before stamping. Therefore, lubricated steel sheet should have good corrosion resistance, and excellent lubricity. With the improvement of environmental protection and energy saving requirements, researchers are trying to improve the lubricating coating from a twice coating style containing a chromium passivation layer to a once coating style without chromium, but all of the current commercial and literatures appeared are weakly acidic aqueous lubricant thermal curing system. This paper aims to develop a lubricating thermal curing coating with aqueous alkaline system without chromium, we prepared water-based lubricated galvanized sheet and studied the curing kinetics of this lubricated coating system. In addition, we developed a water-based UV curing lubricated coating, prepared water-based UV curing lubricated galvanized sheet, and had a research for the UV-curing kinetics of the system. Specific studies and results are as follows:.Silica sol modified by a coupling agent was selected as raw material to prepare water-based thermal curing lubricated coating and prepared a water-based lubricated galvanized steel sheet, which corrosion resistance of neutral salt spray test is more than120h, fingerprint resistance and adhesion are also good and lubricity of lubricated galvanized sheet is better than pure zinc coated sheet with lubricating oil and grease.Effects of the polyethylene wax on the lubricated galvanized sheet were studied. When smaller particle size(0.1μm) of the polyethylene wax is used as lubricant, the friction coefficient of the lubricated coating of galvanized sheet prepared is more stable. Lubricated galvanized sheet with smaller lubricant particles has good corrosion resistance. In the range of4%to20%, with the increase of lubricant content, friction coefficient first decrease and then increase slightly, relatively less lubricant content has poor corrosion resistance.Laboratory studies of the effects of nano-SiO2content on the main properties of the lubricated coating were made. The results show that with the increase of nano-SiO2content corrosion resistance and lubricity of water-based lubricated galvanized sheet first increase and then decrease. There is a best corrosion resistance at the content of16.6%and a lubricity with the best stability at the content of11.4%. Nano-SiO2content has little effect on the drawing ratio with successful completion.Thermal curing kinetic equation of water-based thermal-curing lubricated coating system was calculated through DSC and TG results by different heating rates method. The addition of nano-SiO2decreases the apparent activation energy and apparent frequency factor, increases the reaction order. Curing condition of the coating system was preliminary identified. With the increase of nano-SiO2content the curing reaction rate decreases.Water-based ultraviolet (UV) curable lubricating fluid and water-based UV curing lubricated galvanized sheet were prepared. The effects of nano-SiO2content on the properties of lubricated galvanized sheet were studied. The results show that with the increase of nano-SiO2content, the corrosion resistance first increases and then decreases, at the content of16.6%, the corrosion resistance of the coating is the best. The initial friction coefficient has direct impact on the formability of the lubricated galvanized steel sheet.The conversion rate of the coating system were proved to be decrease because of the addition of nano-silica nanoparticles through both real-time FTIR and photo-DSC methods, and the addition of nano silica increased the reaction diffusion resistance.