Magnesium Phosphate Cement Coating On Metal-based Material Surface

This article is designed to acid-base reaction of different ratio of magnesium-phosphate cement binder coating, applied to the surface of 45 steel.we use special mold to control the th-ickness of the coating. Cross-section shape and the microstructures of the magnesium phosph-ate cement coating were observed by using stereoscopic microscope and scanning electron mic-roscopy (SEM), X-ray diffraction (XRD) were used to measure the components of thecoatings. Discussed different ratio of the microstructure and properties of the coating.In the four kinds of ratios, we studied phosphorus and magnesium ratio P:Mg=1:1.5 (molar ratio) and P:Mg= 1:4 (molar ratio) of magnesium phosphate cement coating which have added sodium silicate and phosphorus and magnesium ratio P:Mg=1:1.5 and P:M g= 1:4 of magnesium phosphate cement coating which haven’t added sodium silicate.The r-esults showed that, under low magnification stereo micros-cope observation, Coating is formi-ng with granular together; under high magnification scanning electron microscope, we observed that the structure of magnesium phosphate cement coating which didn’t add sodium silicate pr-esent flaky, the structure of magnesium phosphate cement coating which added sodium silicate present particles blocks,.and the coating structure is more compact. By scratch test, within a c-ertain time, magnesium phosphate cement coating which pho-sphorus and magnesium ratio is 1:1.5 have a faster self-healing function than magnesium phosphate ratio which is 1:4.We test magnesium phosphate cement coating corrosion resistance by salt spray corrosion test and electrochemical methods. In the salt spray corrosion test, the results show that 45 steel which through professional painting corrosion resistance is about seven times than 45steel whic-h without any processing,four kinds of 45 steel which paint magnesium phosphate cement coati-ng don’t have any signs of corrosion occurred within 720 hours in neutral salt spray corrosion t-ank. Indicating that, painted magnesium phosphate cement coating have good protection against corrosion for 45 steel. In electrochemical experiments, Self corrosion potential of 45 steel w-hich painted four kinds of magnesium phosphate coating increased by 147mv,215mv,119mv and 224mv than 45steel without any processing, Self corrosion potential of 45 steel which paint ed magnesium phosphate cement coating with sodium silicate increased more than 45 steel wh-ich painted magnesium phosphate cement coating without sodium silicate. The corrosion current density of 45 steel which painted phosphorus and magnesium ratio is 1:1.5 increased by two orders of magnitude than 45 steel without any processing.The corrosion current density of 45 st-eel which painted phosphorus and magnesium ratio is 1:4 increased by three orders of magnet- ude than 45 steel without any processing. From the point of the elect-rochemical impedance, cor-rosion resistence of 45 steel which painted magnesium phosphate ce-ment coating improved sig-nificantly than 45steel without any processing, corrosion resistence of 45 steel which painted magnesium phosphate cement coating with sodium silicate significantly better than 45 steel which painted magnesium phosphate cement coating without sodium silicate.Within 720h of salt spray corrosion test,t-here was no significant difference for the four kind-s of magnesium phosphate cement coating pro-tects 45 steel from corrosion; from the point of ele-ctrochemical,the corrosion resistance of 45 steel which paint phosphorus and magnesium ratio P :Mg= 1:4 magnesium phosphate cement coat-ing is better than that of phos-phorus and mag-nesium ratio P:Mg=1:1.5 magnesium phosphate cement coating.