Study On Preparation And Anticorrosion Performance Of Magnetic Gradient Self-healing Coating

In the process of oil and gas storage and transportation,the anticorrosive coating of related equipment is easy to suffer from external mechanical damage and failure.In order to meet the anti-corrosion needs of the field,a variety of self-repairing coatings have been developed,including self-repairing coatings carrying both healing agents and inhibitors.In the process of defect repair,it is easy to have some problems,such as insufficient filling of healing agent,incomplete passivation film of inhibitor and so on.Increasing the amount of microcapsules is a simple and effective way to improve the repair effect of the coating,but it will inevitably introduce more microdefects in the coating,which will have side effects on improving the anti-corrosion performance of the coating and increase the manufacturing cost of the coating.it is not conducive to the large-scale popularization and application of self-repairing coating.Inspired by the delivery function of targeted drugs,the targeted magnetic graphene oxide(MGO),was added into the microcapsules through the guidance of the external magnetic field to achieve the orderly distribution of the microcapsules in the vulnerable parts of the coating,forming a magnetic gradient coating structure in which the linseed oil microcapsules were distributed on the upper surface of the coating and the magnetic benzotriazole(BTA)microcapsules were concentrated on the metal surface.The main research work and results are as follows:First of all,the effects of initial pH value,stirring rate,type and dosage of emulsifier,core-wall ratio and nano-particle content on the morphology,particle size and coating rate of microcapsules were investigated by experiments.the best preparation technology of linseed oil microcapsule and magnetic BTA microcapsule was obtained.the prepared microcapsule had regular morphology,uniform particle size distribution,good barrier property of wall material and high thermal stability,and the average diameter was 80 μm.The coating rate is as high as 85.26wt%.Secondly,common self-repairing coatings(random distribution of microcapsules)and magnetic gradient coatings(ordered distribution of microcapsules)were prepared,and the self-repairing properties of magnetic gradient coatings were studied by scratch experiment.it is found that the self-repairing effect of scratch is enhanced with the increase of repair time and microcapsule content.When the repair time reaches 4 hours,the repair of scratches has been completed by more than 99%.The anticorrosive properties of the two were studied by salt spray test and electrochemical test.It is found that the self-repairing coating with orderly distribution of microcapsules has better self-repairing and anti-corrosion properties when the content of microcapsules is low(≤ 15wt%).This study achieves a significant economy by reducing the amount of microcapsules on the premise of maintaining or even improving the self-repairing and anti-corrosion properties of the coating.