Study On Preparation And Properties Of Waterborne Epoxy Resin Anticorrosive Coatings

As the most direct and economical means of metal corrosion protection,coating anti-corrosion is widely used in transportation,petrochemical,marine engineering and construction engineering industries at domestic and overseas.However,metal anti-corrosion coatings are mainly concentrated on oil-based anti-corrosion,and there are a series of environmental pollution and safety problems.In the field of metal heavy-duty anti-corrosion research and application,there is a big gap in the technology between domestic and foreign countries.In order to comply with the development of water-based anti-corrosion coatings and to narrow the gap with foreign heavy-duty anti-corrosion fields,this paper intends to focus on the current oil-based epoxy zinc-rich anticorrosive coatings for heavy-duty anti-corrosion coatings on metal surfaces.Preparing the waterborne epoxy resin emulsion by phase inversion method,which based on the synthesis of waterborne epoxy emulsion special emulsifier.Then prepare and study the antiseptic properties of the waterborne anti-corrosion zinc-rich coating.Firstly,the esterified products with hydrophilic segments and carboxyl groups was obtained by esterification reaction which used different molecular weight polyethylene glycol(PEG)and phthalic anhydride(PA),and then the ring-opening reaction occurs with the catalysis triphenylphosphine.And the epoxy resin molecules were introduced into the structure to obtain the waterborne epoxy emulsifier which has good compatibility with the epoxy resin.The effects of reaction temperature and catalyst type on esterification and ring-opening reaction were investigated.The structure and molecular weight of the target product were analyzed by infrared spectroscopy and gel permeation chromatography.The relevant parameters of the target emulsifier were characterized,and then initially investigated the emulsify effect of the emulsifier.The results show that the esterification rate can reached at 94.5%without catalyst,the reaction temperature was 110°C,and the reaction time was 3.5 h.At the same time,triphenylphosphine was used as the catalyst,and the ring opening can be completed well at 110°C.The results of infrared spectroscopy and gel permeation chromatography confirmed that the prepared emulsifier had the expected structure;the cloud point and surface tension test results show that the target product has the characteristics of non-ionic emulsifier,which can effectively reduce the surface tension of water;When the dosage was not less than 12.5%,the emulsifier which was synthesized by PEG-6000can prepared a waterborne epoxy emulsion with a particle size of 735 nm,uniform size and good stabilitySecondly,this paper systematically studied the phase inversion process and conditions of epoxy resin E-44 with waterborne epoxy emulsifier,and optimized the techniques of the phase inversion process,and then obtained a stable waterborne epoxy emulsion.A waterborne epoxy zinc-rich anticorrosive coating was prepared by using zinc powder as a sacrificial anticorrosive filler,and the stability and anticorrosion performance of the coating were studied.The results show that at different phase inversion temperatures,there was a sudden change in the electronic conductivity of the system during the phase inversion.The emulsion particle size first becomes smaller and then becomes larger with the increase of the temperature and the dispersion rate,when the phase inversion temperature was 60°C,and the rotation speed was 2500 r/min,the best performance waterborne epoxy emulsion can be obtained.Considering the stability of emulsion,water resistance of film and drying time of film,the dosage of emulsifier should be 12.5%~15%.When the curing agent is polyetheramine D230 and the molar ratio of epoxy to active hydrogen was 1.2~1.0,the obtained coating has good hardness,water resistance and neutral salt spray resistance.When the dosage of wetting dispersant BYK-190 was 3%,the dosage of thickener RM2020 was 2%,and zinc powder accounts for 70%of dry film,waterborne epoxy zinc-rich anticorrosive coatings have good storage stability and viscosity;The anticorrosion performance of different zinc powder coatings was studied by electrochemical workstation and salt spray tester.It was found that when the amount of zinc powder reached 70%,the coating impedance reached4.7×10~6?,and the neutral salt spray did not change for 240 h.The coating has good corrosion resistance.