Preparation Of Waterborne Polyacrylate/Zinc Oxide Microcapsule Composite Coating And Its Corrosion Resistance

Metal corrosion has caused significant safety hazards and huge economic losses.Coating protection methods are widely used to protect metals from corrosion because of their energy saving and simple operation.Waterborne polyacrylate coating has become a promising anticorrosive coating.However,its poor water resistance limits the corrosion resistance.Micro-nano capsules with high specific surface area can fill pores and repair defects in the coating.In a previous study,our team prepared benzotriazole@zinc oxide(BTA@ZnO)microcapsules.However,the amount of BTA@ZnO microcapsules introduced into polyacrylate coating was small and the release behavior was poor.Therefore,the corrosion resistance of the composite coating was limited.Based on this,on the one hand,the layer-by-layer spraying method was applied to study the effects of the position and amount of BTA@ZnO microcapsules in the waterborne polyacrylate coating on the properties of the composite coating,thereby increasing the amount of BTA@ZnO microcapsules introduced into the coating.On the other hand,nitrogen-doped carbon dots@zinc oxide(NCD@ZnO)microcapsules with environmental responsiveness were prepared by a one-step encapsulation method.Then,waterborne polyacrylate/NCD@ZnO microcapsule composite coating was prepared by physical blending method and layer-by-layer spraying method,respectively.Built on the above studies,the following results were obtained.The composite coating with excellent corrosion resistance was successfully prepared via layer-by-layer spraying method.When the amount of aziridine crosslinker was 7.0 mg/cm2 and the amount of BTA@ZnO microcapsules was 2.5 mg/cm2,the composite coating with a mixture of waterborne polyacrylate emulsion and aziridine crosslinker as the bottom layer and BTA@ZnO microcapsules as the top layer had the best comprehensive performance.It shows good adhesion(Grade 0),well pencil hardness(4 H),high water contact angle(156.4 ± 3.8°)and excellent corrosion resistance(6.11×105 ?·cm2).When the amount of aziridine crosslinker was 30.0 mg/cm2 and the amount of BTA@ZnO microcapsules was 1.7 mg/cm2,the composite coating obtained by spraying waterborne polyacrylate emulsion,aziridine crosslinker and BTA@ZnO microcapsules in sequence had the best comprehensive performance.It shows good adhesion(Grade 0),well pencil hardness(4 H),fine water contact angle(84.0 ± 4.7°)and excellent corrosion resistance(2.13×105 ?·cm2).Nitrogen-doped carbon dots(NCDs)with a size distribution of 3?8 nm were successfully prepared by solvothermal method.When the dosage was 20 mg/L,it had the best corrosion resistance(1.92×103 ?·cm2).NCD@ZnO microcapsules were fabricated by a one-step encapsulation method using NCDs as the core material and nano-ZnO as the wall material.Their size was 100?200 nm and the loading efficiency was 34.69±3.04%.NCD@ZnO microcapsules had good release performance for NCDs in salt solutions of different concentrations,and their slow release performance was conducive to the improvement of corrosion resistance.The waterborne polyacrylate/NCD@ZnO microcapsule composite coating was prepared by physical blending method.When the dosage of NCD was 0.07%and the amount of the prepared NCD@ZnO microcapsules was 3.0%,the composite coating had good adhesion(Grade 0),well pencil hardness(3 H)and fine corrosion resistance(2.74×103?·cm2).When the amount of NCD@ZnO microcapsules was 0.1 mg/cm2,the composite coating with NCD@ZnO microcapsules as the bottom layer and a mixture of waterborne polyacrylate emulsion and aziridine crosslinker as the top layer had the best comprehensive performance.It shows good adhesion(Grade 0),well pencil hardness(4 H)and excellent corrosion resistance(1.53×106?·cm2).