Preparation Of New Type Rust Agent And Waterborne Rustconversion Coating

In this paper, a water-based rustconversion emulsion based on polymer resin wasdeveloped. The research work in this thesis mainly consisted of the following twoaspects: preparation of functional gallic acid ester and synthesis of functional acrylicrustconversion emulsion.(1) Gallic acid ester was synthesized by using an epoxy ring-openingesterification method, with methylacrylic acid glyceride shrink as raw materials,gallic acid as functional monomers. It was demonstrated that when the proportion ofmethylacrylic acid glyceride shrink and gallic acid was4:1and the mixturetemperature was set at110℃, the as-synthesized esterification products werepolymer rust agent, which was golden in color and had excellent turned rustperformance. Rust could be converted into black materials within20minutes bybrushing this ester to the corroded steel plates. A rust agent function test of steelanticorrosive property through Tafel polarization curve method were also performed.The results showed that the corrosion potential of the conversion coating compared tothe bare electrode is significantly larger. And when n=4:1, the Corrosion current wasthe least. Through the infrared spectrum diagram analysis, the structure of rust agentand conversion coating were determinated. The results showed that the molecularchain of rust agent consisted of polyphenol structure and lively carbon-carbon doublebond, but the position and intensity of several absorption peaks in membrane afterturning rust changed, which proved rust reacted with rust agent. The rusty layer wasanalyzed by SEM in order to determine the amorphous change after turning rust. Wefound that the rust layer after turning rust was compact, which could effectivelyprevent the corrosion. The iron electronic change was studied by the XPS spectrumdiagram, and we speculated that Ortho phenolic hydroxyl group contained in turn rustmolecules reacted with Fe2+/Fe3+contained in rust to form complexes, in which turnrust agent with Fe3+formed much more stable complexes.(2) Using acrylic monomers as raw materials, gallic acid ester as functionalmonomer was synthesized by seed emulsion polymerization method, then ammoniumpersulfate as the initiator, sodium dodecyl sulfate and OP-10as compound emulsifier,a single-component water-based rust paint was formed by the continuously seed emulsion polymerization method. In order to determine the optimum reactioncondition, the influence of gallic acid esters’ contents, molar ratio of sodium dodecylsulfate and OP-10, ratio of acrylic monomers in the reaction system on theperformance of water-based acrylic emulsion were investigated. A water-basedacrylic emulsion function test of steel anticorrosive property through the saline soakmethod and Tafel polarization curve method were also performed. The results showedthat the film almost did not change after being soaked in3.5%NaCl solution within72hours, and the corrosion potential of the coating is significantly higher than thebare electrode. And when MMA: BA was1:1and the content of intermediate was5%,conversion coating has the highest corrosion potential and the smallest corrosioncurrent. In the present work, the water-based antirust emulsion does not containorganic solvents, which can be cured at room temperature, with dry time of less than30minutes and turning rust speedy. It can transform20μm rusts completely in20minutes and has no bubbles falls off in phenomenonsaline for three days. Therefore, ithas a good prospect of application.