Preparation Of Corrosion Inhibitor Microcapsules And Anti-Corrosion Performance Of Self-Healing Coating

Metal anti-corrosion has always been a hot topic in academic research.The most simple and effective anti-corrosion method is to spray a layer of coating on the surface of metal matrix.Because the coating is easy to be affected by the environment in the process of use,microcracks appear.After microcracks occur in the coating,corrosive media such as seawater and air will enter the coating from the crack and reach the surface of the metal matrix to cause corrosion of the metal.Adding microcapsules with self-healing anti-corrosion function to coatings can effectively solve the problems in the practical application.In this paper,two p H responsive microcapsules loaded with corrosion inhibitors were prepared by solvent volatilization and vacuum impregnation,and the self-healing coating containing microcapsules was prepared at the same time.The purpose is to make the coatings have good corrosion resistance to the metal substrate through the synergistic effect of corrosion inhibitor and polydopamine.Meanwhile,the anti-corrosion mechanism of microcapsule self-healing coating was discussed,which has important reference value for the research and application of metal corrosion protection.The main contents of this article can be summarized as follows:（1）Using corrosion inhibitor 8-hydroxyquinoline（8-HQ）as core material,polysulfone（PSF）and polydopamine（PDA）as wall material,the 8-HQ@PSF microcapsule was prepared by solvent evaporation method,and the PDA outer layer was loaded on the surface of the microcapsule by self-assembly method,and the 8-HQ@PSF/PDA self-healing microcapsule was successfully prepared.By studying the kinds of surfactants,reaction stirring rate and the influence of core wall ratio on the preparation of microcapsules,the optimal synthesis conditions were determined:Lignosulfonate（Reax-88A）was selected as the surfactant,the concentration was 2wt.%;the reaction stirring rate was 800 r/min;the core wall ratio is 2:1.The microcapsules had rough surface and nearly spherical structure,with an average particle size of 12.3μm and wall thickness of 1-2μm.Microcapsules had good thermal stability,the core material content is about 61.0 wt.%.UV-Vis analysis showed that 8-HQ@PSF/PDA self-healing microcapsules had p H response release.The self-healing epoxy coating was prepared by adding microcapsules to epoxy resin.By comparing the corrosion of epoxy coating with different contents of microcapsules,the optimal addition amount of microcapsules for the self-healing anti-corrosion coating was determined to be 5wt.%.The impedance modulus of the coating at 0.01Hz remains about 10⁴Ω·cm²after 30 days of immersion in 3.5wt.%Na Cl solution.Meanwhile,the synergistic anticorrosion mechanism of core material and wall material is revealed.（2）With tannic acid（TA）as core material,hollow mesoporous silica（HMSNs）and PDA as wall material,HMSNs were prepared by sol-gel method,and then TA@HMSNs microcapsules were prepared by vacuum impregnation method.Finally,the loaded PDA layer was self-assembled in situ on the surface of microcapsules.TA@HMSNs/PDA self-healing microcapsules were successfully prepared.By studying the effects of cetyltrimethylammonium bromide（CTAB）dosage,reaction agitation mode and core wall ratio on the preparation of HMSNs,the optimum synthesis conditions of HMSNs were determined as follows:CTAB dosage is 0.8g;the reaction agitation mode is mechanical agitation;the core wall ratio is 2:1.N₂adsorption and desorption isotherm analysis showed that the specific surface area of HMSNs was 1151.696 m²/g,the average pore size was 3.66nm,and the pore volume was 1.222 cm³/g.The average particle size of TA@HMSNs/PDA microcapsules is about 530 nm.Good thermal stability,core material content is about23.1wt.%.UV-Vis analysis showed that TA@HMSNs/PDA self-healing microcapsules had p H response release.The microcapsule self-healing anti-corrosion epoxy coating was prepared and its self-healing anti-corrosion performance was tested.The results show that the epoxy coating with microcapsules has good anti-corrosion performance,and the impedance modulus at 0.01Hz is still close to 10⁵Ω·cm²when after soaking the scratch coating which added 5wt.%microcapsules for 30 days.