Preparation Of Micro-Nano Container Loaded With Corrosion Inhibitor For Self-Healing Anticorrosive Coating

The common phenomenon that metal materials are damaged due to corrosion has a certain impact on the production activities of various industries.Coating on the metal surface is an effective way to solve the problem of metal corrosion.However,the coating can only protect the metal for a short time.Due to the long-term exposure of the metal in the corrosive environment,the influence of external stimuli such as pH,temperature and light is intensified,resulting in microcracks.Corrosion medium such as water and air will successively enter the coating through cracks and reach the metal substrate to corrode it.Coating a self-healing coating on the metal surface can increase the long-term protection of the metal substrate to a certain extent.In this paper,three kinds of self-healing microcapsules loaded with corrosion inhibitors were prepared by impregnation method and template method,and self-healing composite coatings were prepared.The composite coating has good corrosion resistance to carbon steel substrate,and has important reference value for corrosion protection research in metal application field.（1）BTA@DME were first prepared by vacuum impregnation method with benzotriazole（BTA）as the core material and diatomite（DME）as the micro-nano container,the pH-responsive BTA@DME/PDA self-healing microcapsules were successfully prepared by self-assembly of pH-responsive polydopamine（PDA）outer layer on its surface.By comparing the effects of different impregnation methods on the preparation of microcapsules,it was finally decided to prepare microcapsules by vacuum impregnation method,and the prepared microcapsules had a high loading rate.The specific surface area of DME was 3.796 m²/g,the pore volume was 0.005 cm³/g,and the average pore size was 51.74 nm.The surface of DME was rough and disc-shaped,with an average particle size of about 25μm and a wall thickness of about 2μm.The thermal stability is good,and the core material content is about 46.3wt.%.UV-Vis analysis showed that BTA@DME/PDA self-healing microcapsules had pH-responsive release.The self-healing epoxy coating was prepared by adding microcapsules to epoxy resin.By comparing the corrosion of epoxy coatings with different contents of microcapsules,the optimum addition amount of microcapsules for the self-healing anticorrosive coating was determined to be 5wt.%.The impedance modulus of the coating remained at about 10⁵Ω·cm² at 0.01 Hz after immersion in3.5wt.%NaCl solution for 30 days.（2）BTA@DME were first prepared by vacuum impregnation method with BTA as the core material and DME as the micro-nano container,the pH-responsive BTA@DME/Cu²⁺-BTA self-healing microcapsules were successfully prepared by loading Cu²⁺-BTA pH-responsive outer layer on the surface of microcapsules.The microcapsules have good thermal stability,and the core material content is about44.6wt.%.UV-Vis test proved that BTA@DME/Cu²⁺-BTA self-healing microcapsules had pH-responsive release.By comparing the self-healing and anticorrosive properties of epoxy coatings with different microcapsule additions,the optimal addition of microcapsules for the self-healing anticorrosive coating was determined.The scratch coating with 5wt.%microcapsules was immersed in 3.5wt.%NaCl solution for 30 days,and the impedance modulus at 0.01 Hz was maintained at about 10⁶Ω·cm²,which had the best anti-corrosion effect.（3）BTA@HMCs/PANI microcapsules were prepared by using corrosion inhibitor BTA as core material,hollow mesoporous carbon spheres（HMCs）as micro-nano containers and PANI as coating layer.Firstly,HMCs were prepared by template method,then BTA@HMCs microspheres were prepared by vacuum impregnation method,and finally BTA@HMCs/PANI microcapsules were prepared by in-situ polymerization.By comparing the effects of different alcohol-water ratios on the preparation of microcapsules,it was found that the microspheres prepared when the alcohol-water ratio was 9:1 had relatively good morphology.The specific surface area of HMCs was346.716 m²/g,the pore volume was 0.521 cm³/g,and the average pore size was 6.011nm.The average particle size of BTA@HMCs/PANI microcapsules was about 270 nm.The thermal stability is good,and the core material content is about 31wt.%.The microcapsule self-healing anticorrosive epoxy coating was prepared and its self-healing anticorrosive performance was tested.The results show that the epoxy coating with microcapsules has good corrosion resistance.After 30 days of immersion in the scratch coating,the impedance modulus at 0.01 Hz still exceeds 10⁵Ω·cm² when 5wt.%microcapsules are added.At the same time,the synergistic anti-corrosion effect of the wall material PANI and the core material BTA is discussed.