Study On Self-curing Inorganic Phosphate Anticorrosive Coatings At Ambient-temperature

Phosphate anticorrosive coating, which belongs to inorganic coating, has aroused extensive concern in the cases of its high-temperature resistance, oxidative resistance, strong adhesion, corrosion resistance and non toxicity. However, one of its main shortcomings is that phosphate coating can not cure slowly at low temperature or ambient-temperature. In this study, alkali metal oxide curing agent was synthesized by using surface coating technology of nano-particles, and then we realized curing of phosphate coating at low temperature (80℃) and ambient-temperature. Also, the curing mechanism was studied further.Firstly, phosphate binder (film-forming resin) was prepared by A1(OH)3and H3PO4, MgO burned at high temperature was used as curing agent. The ratio of raw materials, synthetic conditions of the binder and the coating were studied. The results showed that A1(H2PO4)3could be synthesized with Al/P=1.2-1.4:3at140-160℃. And the hardness of coating reached6H with P/Mg=3.5-4:1.Secondly, A kind of low-temperature curing inorganic phosphate coating which was composed of phosphate adhesive (film-forming resin) and MgO@SiO2(curing agent) were prepared. MgO@SiO2, as curing agent, was derived by surface coating mechanisms of nano-particles. By using relevant characterization methods, the curing mechanism of the coating was also explored. Results show that, by selecting MgO@SiO2as curing agent of the phosphate coating, the curing time of the inorganic phosphate coating was extended from tens of seconds to120mins, and the curing temperature was decreased to80℃. The prepared coating also has good moisture absorption resistance and film-forming property.The third, a kind of self-curing inorganic phosphate anticorrosive coating at ambient-temperature was obtained with Al(PO3)3-Fe(PO3)3compound phosphate adhesive and MgO@SiO2-Fe2O3compound curing agent which were treatment with Fe2O3-modified. The curing mechanism and industrial application of the coating were studied by utilizing relevant characterization methods and industrial experiment. The results indicate that the comprehensive performance of the coating was excellent, the adhesive force of the coating reached6MPa, the salt spraying test passes432h, and the adhesive force could still reach2MPa after432h salt spraying test. Then, ambient-temperature curing water-based phosphate anticorrosive coating was painted on rusty surface. Tests revealed that the coating was applied to painting on rusty surface without surface pretreatment, and the performance of corrosion resistance was still excellent. MgO@SiO2, as curing agent, was derived by surface coating mechanism of nano-particles to realize the gradual-release of MgO in the curing process of the coating. Not only it increased the curing time but also decreased the curing temperature of the coating. Its low-temperature curing contains two main stages:condensation polymerization of Al(H2PO4)3and complete curing at80℃. A kind of self-curing inorganic phosphate anticorrosive coating at ambient-temperature was obtained successfully with Fe2O3-modified. Aluminophosphate molecular sieve curing mechanism of the coating was proposed. The proposal of this innovation curing mechanism associates phosphate anticorrosive coating with molecular sieve, and it has important implications for phosphate material.