The Preparation Of Functionalized Boron Carbide And The Corrosion Resistance Of Epoxy Composite Coating

Metal corrosion can cause drilling tool fatigue,seriously threaten downhole safety,and even lead to the abandonment of wells.In order to prevent or reduce drilling tool corrosion,the common anti-corrosion methods in drilling process are adding deoxidizer,desulforizer,corrosion inhibitor,using anti-corrosion coated drilling tools and adjusting the pH value of drilling fluid.The composite coatings have the advantages of low cost,simple operation and excellent anticorrosive effect.However,in the curing process of epoxy resin at high temperature,the volatilization of-solvents will result in very small pores or connected channels,which greatly limit the use of anticorrosive coatings.In recent years,the preparation of inorganic-polyler composites using inorganic nano-materials and epoxy resin is one of the research hotspots of composite anti-corrosion coatings.Inorganic nano-fillers have excellent physical and chemical properties and can greatly improve the corrosion resistance of epoxy resin when well dispersed in the resin.The thermal stability and corrosion resistance of nano-filler/polymer composite coatings were studied in this paper.Boron carbide with excellent physical and chemical properties was used as inorganic nano-filler to prepare boron carbide/epoxy resin composites.The properties of the composites are closely related to the dispersion and interfacial compatibility of boron carbide.Boron carbide is not uniformly dispersed in polymer and easy to agglomerate,which results in the weakening of the interaction force of polymer and limits its performance.Therefore,the surface modification of B4C is the key to show the superior properties of composites.In order to give full play to the role of nano-materials in polymer,different modification methods such as physical coating,small molecule grafting,magnetic material loading were used to modify the surface of boron carbide,functional boron carbide was obtained,and B4C/EP composite coating with excellent performance was prepared.The effects of modified nano-fillers on the electrochemical properties and thermal stability of epoxy coatings were studied by means of cross-section scanning electron microscopy,TGA thenmogravimetric test,salt spray test and high temperature and high pressure test,and the anticorrosion effect of the composite coatings in drilling fluid environment was preliminarily explored.The results show that:(1)B4C-PDA composites were prepared on the surface of boron carbide by self-p olymerization of dopamine to coat polydopamine(PDA),which improved the compatib ility and interfacial bonding ability between nano-fillers and epoxy resin,solved the ag glomeration phenomenon of nano-fillers in polymer,improved the dispersion of boron carbide in coatings,and effectively enhanced the thermal stability and electrical propert ies of B4C-PDA/EP.The chemical properties and the corrosion resistance of B4C-PDA/EP in drilling fluid environment were preliminarily studied.(2)B4C-KH550 composites were prepared by grafting amino groups on boron car bide surface,which improved the dispersion of nano-fillers in epoxy resin.The conpa tibility between boron carbide and epoxy resin was enhanced by the introduction of s mall molecular amino groups,and the agglomeration of boron carbide in polymer was solved.Thermal stability and electrochemical properties of B4C-KH55O/EP composite coatings were improved.At the same time,the anticorrosion effect of composite coati ngs in drilling fluid environment was preliminarily explored.(3)B4C-PDA-Fe3O4 hybrid material was prepared by immobilizing Fe3O4 particles on boron carbide surface by hydrothermal method using dopamine-coated boron carbi de as template and adding appropriate amount of precursor(FeCl3·6H2O).The compa tibility and interfacial bonding ability between boron carbide and epoxy resin were im proved,the agglomeration of B4C was effectively reduced,and the dispersibility of B4 C in epoxy resin was improved.The thermal stability and electrochemical properties o f B4C-PDA-Fe3O4/EP were studied,and the corrosion resistance of B4C-PDA-Fe3O4/EP in drilling fluid environment was preliminarily explored.