Research On Magnesium Potassium Phosphate Coating Modified By Quartz Sand And Glass Fiber

In the marine environment,the corrosion rate of steel structures accelerates,causing serious structural damage and economic losses.Therefore,the corrosion preventions are necessary.Coating protection is one of common methods for corrosion preventions in steel structures.However,in special environments such as offshore launch sites,the anti-corrosion coating can crack and peel off,losing its anticorrosion function.This thesis focuses on the significant demand for steel structure protections in the combined thermal shock and salt fog environment,and explores the heat-resistant,anti-corrosive,and mechanical properties of magnesium potassium phosphate coatings applied to steel structures.Furthermore,to solving the current problems with magnesium potassium phosphate coatings,quartz sand and glass fiber were added into the phosphate coatings.The results show a feasible approach to enhance the corrosion resistance and prolong the service life of steel structures under the thermal shock and salt fog environments.The main research contents and results are as follows:(1)In the raw material of magnesium potassium phosphate(MKP),the influence of the particle sizes of magnesium oxide(MgO)on the hydration reaction process of MKP is explored.The setting time,compressive strength,pore structure and early hydration heat of MKP briquette with different particle sizes of MgO are systematically studied,and the optimal MgO particle size and raw material ratio are obtained,which provides the basis for the subsequent experiments.(2)Aiming at the problem that the coating is easy to fall off the steel structures in the process of thermal shock,the influences of different kinds and different proportions of admixtures on the mechanical properties and corrosion resistance of MKP coating are systematically studied.It is found that the bonding strength of MKP coating can be greatly improved by adding a certain amount of quartz sand or glass fiber into the MKP coating.Studying the stability of the optimized MKP coatings,the various properties and pore structures of the MKP coatings with different proportions and curing ages are explored.The results suggest that both the initial proportion of MKP coating and the optimized MKP coating can reach the stability after curing for 7 days in a dry environment at room temperature,which provides the basis for the thermal shock experiment.(3)Neutral salt spray test and electrochemical test show that the corrosion resistance of MKP coating test plate is kept well after adding quartz sand and glass fiber.Meanwhile,the MKP coatings with different proportions in salt spray environment continue to undergo hydration reactions to achieve self-healing ability.(4)The thermal shock cycle tests of different MKP coated plates are carried out in Muffle furnace at high temperature.The thermal shock resistances of the three groups of coatings are compared through observing the coating morphologies and testing the mechanical properties.After the thermal shock cycles,the three groups of MKP coated plates are impregnated with NaCl solution.The corrosion resistances of MKP coatings after thermal shock cycles are evaluated by the substrate morphology observations and electrochemical tests.It demonstrates that the thermal shock resistances of MKP coatings are enhanced after adding quartz sand and glass fiber,and the three groups of MKP coatings still preserve good self-healing performance after thermal shock cycles..