Study On Preparation And Properties Of Waterborne Rust Conversion Coatings

A waterborne rust conversion coating which can be coated on steel with rust layer was prepared by using organic acids such as tannic acid as rust material,citric acid and borate as complexing agents,styrene-acrylic emulsion and modified styrene-acrylic emulsion as film-forming material,and then adding film-forming auxiliaries to prepare a waterborne rust conversion coating on steel with rust layer.The optimum formula of the coating was determined by orthogonal test and single factor test,and the viscosity,surface tension and drying time of the waterborne rust conversion coating before coating were tested.After the paint film was formed,the anticorrosion rate was characterized by salt fog resistance,salt water resistance and Tafel test,and the optimum application conditions of waterborne coating were determined.the properties of the paint film were determined by adhesion measurement and contact angle measurement.and its apparent and microscopic properties were determined by scanning electron microscope(SEM)and infrared spectroscopy(IR).The optimum formula of waterborne rust conversion coating was determined by orthogonal test and single factor test as follows:film forming material 65%,rust conversion agent 5%,rust promoter 2%,corrosion inhibitor 0.6%,osmotic agent 2%,citric acid 0.5%and film forming agent 1.6%,and the rest were distilled water.The storage stability of waterborne rust conversion coating is good,the surface tension of the coating is 33.17 mn/m;the viscosity is 10.2mPa·s,and the coating has good wettability and flowability.The coating temperature range is 20℃～40℃,the thickness of rust layer is 20 μm,the coating amount is 0.375 kg·m2,the adhesion of paint film can reach the first level,and the coating can completely transform the rust layer to form a dense protective film.The waterborne rust conversion coating can be coated on different iron and steel materials and tested on the surface of spring steel and Q235 carbon steel.After coating,a dense and continuous protective paint film is formed.Through the weather resistance test,it is confirmed that the paint film has good corrosion resistance and has a wide range of applications.Through thermogravimetric test,the weight loss of the paint film below 220℃ is less than 6%,which has good stability and can meet the requirements of daily use.The corrosion resistance of rust coating was studied by electrochemical workstation and neutral salt spray test,and compared with that of rust coating.The results show that the waterborne rust conversion coating can be resistant to salt fog(5%)96h,salt water resistance(3.5%)168h,and the paint film is not destroyed without corrosion.Through the acid and alkali corrosion resistance test,the paint film has good acid resistance,and the paint film is not destroyed in the corrosion solution of ph 2,which has protective effect.Compared with the rust coating sold in the market,the self-made coating has better film compactness and stronger corrosion resistance.The product is a water agent,which can be coated directly on the surface of rust steel plate to avoid the environmental pollution caused by acid rust removal process in industry.It is a kind of environmental protection coating,which has good environmental benefit and market application prospect.