Study On The Properties And Mechanism Of Phosphate Inorganic Anticorrosive Coatings

Inorganic phosphate coatings are high performance material,which have high corrosion resistance,good water resistance,high strength,and high metal adhesion.Furthermore,they are low cost with less pollution,compared with organic coatings.Phosphate coating consists of phosphate binder,curing agents and fillers.There are many types of phosphate binders,and the most widely used phosphate matrix is aluminum dihydrogen phosphate.Usually,the formation of phosphate coating needs a certain high temperature,which consumes energy and is cumbersome to operate.In addition,the reaction mechanism of phosphate is not clear.In view of this,this topic aims to improve the curing performance of phosphate anticorrosive coatings at room temperature,using aluminum dihydrogen phosphate solution as a matrix,magnesium oxide,aluminum hydroxide and silica as fillers.The primary performance of the inorganic phosphate coating was studied.The results obtained mainly include as the followings:（1）The suitable mix formula of phosphate anti-corrosion coating.The mass fraction of aluminum dihydrogen phosphate solution,aluminum hydroxide,silica,and magnesium oxide was used as a control parameter,and the mechanical properties and setting time of the phosphate anti-corrosion coating were used as the measurement indexes.For obtain the excellent inorganic phosphate anti-corrosion coating and the performance was finally prepared by orthogonal test.（2）Phosphate anti-corrosion coating formation mechanism.Phosphate inorganic anti-corrosion coating composition with the most suitable mix ratio was selected for further study.The microstructure of phosphate inorganic anti-corrosion coating was observed by XRD,FTIR,and SEM,and the curing mechanism of phosphate inorganic anti-corrosion coating was discussed.The results showed that the solidification of phosphate inorganic anti-corrosion coatings reduced the setting time due to the incorporation of magnesia,and reacted with the phosphate solution to form MgHPO₄·3H₂O.The formation of this kind of crystal improved the microstructure of the material.（3）Silica Sol improves the performance of phosphate anti-corrosion coatings.Silica sol modified phosphate inorganic anti-corrosion coating was prepared with different mix ratios,and the material was subjected to XRD,SEM,FTIR,and hydration thermal analysis tests.The results show that the addition of silica sol can improve the internal structure of phosphate inorganic anti-corrosion coating and make the crystals more compact and complete.Meanwhile,it also reduces the rate of heat release and reduces the total amount of heat release,which is conducive to the formation of crystals and Grow.（4）Corrosion resistance of silica sol modified phosphate inorganic anti-corrosion coatings.Different proportions of silica sol modified phosphate inorganic anti-corrosion coatings were prepared,and the materials were applied to A3 steel for anticorrosive experiments.The results show that the silica sol modified phosphate anti-corrosion coating after 720h neutral salt spray test is still valid,reaching the purpose of preservation.When the coating was subjected to a 30-day acid-base immersion test,the anti-corrosion effect was different in different acid-base solutions,and the protective effect is the best when the pH value was between 5 to 10.In addition to physical protection there is electrochemical protection of the coating.