Preparation And Study Of Phosphate Inorganic Metal Anticorrosive Coatings

The properties of potassium magnesium phosphate cement?MPKC?are similar to those of ceramic after hardening which has high density,high mechanical properties and excellent corrosion resistance to chemicals.It is also called chemical bonded phosphate ceramic material.The strength of potassium magnesium phosphate cement develops rapidly.It has excellent interfacial bonding properties with metals,concrete and wood.It has low permeability,small shrinkage and good salt spray,acid and alkali resistance and high temperature resistance.In this paper,potassium magnesium phosphate cement is used as binder and aluminium tripolyphosphate anticorrosive pigment is added to prepare metal protective coatings with excellent anticorrosive properties.The coatings are mainly used for anti-corrosion of metal materials.Aluminum tripolyphosphate is a new generation of green ecological anti-corrosive pigments with excellent anti-corrosive properties and attracts more and more attention.The corrosion resistance of phosphate inorganic coatings studied in this paper is characterized by testing their physical,mechanical and chemical properties,such as wear resistance,hardness,water resistance,chemical reagent resistance,salt spray resistance,etc.,and verified by accelerated corrosion test.The samples eroded by salt solution were studied by electrochemical method and micro-Characterization method.The mineral composition of the coating was analyzed by X-ray diffraction?XRD?,and the micro-morphology of the interface between the coating and steel was analyzed by scanning electron microscopy?SEM?.The results show that MPKC paste has good anti-corrosion ability,and the addition of anti-corrosion pigments significantly improves the anti-corrosion performance of the later coating.Anti-corrosion pigments have an effect on the bonding strength and hardness of coatings to steel plates.When the content of anti-corrosion pigments is more than 5%and less than 15%,the bonding strength and hardness increase with the increase of the content,while the hardness and bonding strength of coatings decrease when the content reaches 20%,so the content of anti-corrosion pigments should be controlled within 20%.The coating also has excellent salt water resistance,alkali resistance,heat and humidity resistance and temperature variation.The accelerated corrosion test shows that the corrosion resistance of aluminum dihydrogen triphosphate is better than that of aluminum triphosphate and modified aluminum triphosphate.In addition,the anti-corrosion mechanism of phosphate inorganic metal anti-corrosive coating is physical and chemical double protection.The rod-like bird's feces crystals formed by magnesia and potassium dihydrogen phosphate are dislocated and cross-linked to form a dense structure.The unreacted magnesia filling in the pore enhances the integrity of the coating,improves the overall strength,and makes the coating more compact,thus making the physical protection of the coating more compact.The effect has been improved.In addition,PO₄^3-released from potassium dihydrogen phosphate can bind with metal ions,and the P₃O₁₀^5-contained in anti-corrosive pigments has better chelating force with metal,which makes the coating have better chemical protection effect.The results of electrochemical test show that the anti-corrosive coating doped with aluminum dihydrogen tripolyphosphate has better anti-corrosive effect,and the anti-corrosive effect is the best when the dosage is15%.