Synthesis And Application Of New Water-based Rusr Converter And Rust Conversion Coating

Gallic acid is widely used in the preparation of rust-conversion coating due to its multiple phenolic hydroxyl groups which can react with rust.However,as its weak rust-conversion capacity,poor water resistance and low stability,it should be modified.The traditional improvement approach is to be mixed with other organic or inorganic acid which can improve the conversion capacity of rust converter.But in this case,excess acid can introduce a large number of active groups,and then lead to the worse stability and water resistance of the coating.Firstly,a novel water-based rust converter 2-hydroxypropyl 3,4,5-trihydroxybenzoate(named as RC-GAE)was prepared by using an esterification reaction between 1,2-propylene glycol and gallic acid in this study.The rust was converted to a compact black protective rust-conversion film with the rust converter.The anticorrosion performance of the rust converter was investigated by the Tafel polarization curve.The result showed the corroded plate after treated with converter possessed an excellent anticorrosion property.And the optimal mass ratio of PG and GA for the converter was 3:1 as the corrosion potential and corrosion current density of the sample were-0.973 V and 1.195×10-5 A/cm2,respectively.The structure and rust convertion ability of the as-prepared rust converter were conducted by FT-IR.The metallographic microstructure,morphology,and crystalline phase of the rust-conversion films were conducted systematically by optical microscopy,X-ray diffraction,and scanning electron microscopy with energy-dispersive spectrometry.The results show that the corroded plate with uneven and rough brown surface became smoother and darker after treated with converter.X-ray photoelectron spectroscopy indicated that the RC-GAE reacted with Fe2+/Fe2+ and formed a compact Fe2+/Fe3+chelate film that played the role of rust removal,antirust,and anticorrosion.Then,a modified acrylic emulsion copolymer which has good performance was prepared by using the pre-emulsification,semi-batch emulsion copolymerization process between Veova 9,glycidyl methacrylate and other acrylic monomers.The effects of monomer ratio,initiator,emulsifier and polymerization temperature on the preparation of modified acrylic emulsion copolymer were conducted systematically.The as-prepared modified acrylic emulsion was analyzed by FT-IR,and the hardness,adhesion and water resistance of the modified acrylic emulsion copolymer were tested.The results showed that the film performances of modified acrylic emulsion copolymer were good:the hardness,adhesion,impact resistance and water resistance time of the coating film were 2H,grade 1,50 kg-cm and 500 h,respectively.Lastly,a noval water-based anticorrosion coating was prepared by applying a mixture of RC-GAE,modified acrylic emulsion copolymer and other additives to form polymer composites coating on the rusty steel plates.The hardness test,adhesion test and neutral salt spray test were conducted to evaluate the film performances of the coating.The results showed that the film performances of the new water-based anticorrosion polymer composites coating were good:the hardness,adhesion and protection rating in the neutral salt spray test of the coating film were 1H,grade 1 and Rp/240 h=10,respectively.