Study On Preparation Performance And Application Of Water-borne Tolerant Anti-corrosion Coatings For Steel In Harsh Environment

The serious corrosion problem of steel under the chloride environment not only leads to the significant reduction of the safety and durability of building structure,but also is an important factor affecting the project investment benefit and the effective utilization of resources.Therefore,the research on the steel surface anti-rust technology and rusty steel surface treatment technology is the key to reduce corrosion losses,promote the utilization of resources and sustainable development.In this paper,a kind of compound conversion agent which can convert rust layer into corrosion-resistant passivation film layer was prepared.The effects of different pH and neutralizers on the structure and properties of rust layer were studied by optical microscope?OM?,Fourier transform infrared spectroscopy?FT-IR?,electrochemical impedance spectroscopy?EIS?and Ultraviolet and visible spectrophotometer?UV-Vis?.The results show that the compound conversion agent can transform the corrosion products on the surface of rusted carbon steel into a flat and compact passivation film,which can significantly reduce the Fe³⁺precipitation rate on the surface of rusted carbon steel,thus improving the corrosion resistance of rusted carbon steel.After coating compound conversion agent,the main components of conversion film formed on the surface of rusted carbon steel are iron tannate and iron phosphate.When the pH is 3 and neutralizer is specific compound,the rust layer can be completely transformed and the passivation film formed is smooth and compact.Secondly,a long-acting polymer protective coating for producing rust conversion film of corroded steel was prepared by adding the conversion agent into the waterborne vinylidene chloride acrylic resin?VDC-MA?.The influence of the content of compound rust conversion agent on waterborne vinylidene chloride acrylic acid rust conversion coating was studied by means of tensile test,water contact angle,adhesion test?pull-out method?,polarizing microscope?PM?,linear polarization resistance?LPR?and electrochemical impedance spectroscopy?EIS?.The results show that the rust layer can be completely converted and the cross-linking degree of the coating isn't affected obviously when the mixing amount of the conversion agent is 10%.The corrosion current density of coated steel electrode soaked in 3.5%NaCl solution for 30 days was 0.00343?A·cm²,far below the bar corrosion threshold of 0.1?A·cm².And the long-term corrosion resistance of waterborne vinylidene chloride acrylic acid rust conversion coating to corrode steel is obviously improved.Finally,a kind of waterborne two-component polyurethane?WB 2K-PUR?coating was prepared by synthesizing hydroxyl waterborne polyurethane?HO-WPU?and using water dispersive isocyanate?WDPI?as curing agent,and the effect of different ratios of polyester polyols and polyether polyols on the properties of waterborne two-component polyurethane coatings were studied.The characteristics and microstructure of the coatings were analyzed by Fourier transform infrared spectroscopy?ATR-IR?,contact angle,differential scanning calorimetry?DSC?,dynamic mechanical thermal analysis?DMTA?and atomic force microscopy?AFM?.The results showed that the mechanical properties and corrosion resistance of the coating made of polyester polyols and polyether polyols with appropriate proportion are improved significantly.Performance testing of waterborne vinylidene chloride-acrylic rust conversion primer and waterborne two-component polyurethane topcoat composite coating system shows that the primer and topcoat have good compatibility and environmental adaptability.The engineering application examples of using rust conversion agent to repair and protect the corroded steel bars are given.