| With the development of drilling technology,various types of drilling fluids used to meet the needs of various types of drilling technology,which contain a variety of additives and the components are complex,and the drilling tools are highly corrosive under the effect of high temperature and high pressure downhole,while the main thing is electrochemical corrosion.Corrosion of drilling tools not only causes massive scrapping of drilling tools,but also seriously jeopardizes the safety downhole and even results in the rejection of wells which greatly increases production costs.There are many ways of anticorrosive drilling tools,the use of epoxy coatings to carry out anti-corrosion of these materials has simple steps,strong operability,and good results.Due to the volatilization of the solvent during the high-temperature curing process of the epoxy coating,micropores or even connected pores are formed inside the coating,and after solidification,a three-dimensional network structure exists,there is a large internal stress,brittleness,and thermal stability.Poor impact resistance,etc.,lead to a shortened service life of the coating.These unfavorable factors also make it subject to certain restrictions during use.In order to obtain excellent anti-corrosion coatings,nanomaterials are often added as fillers to epoxy resins to improve their properties.The large specific surface area of the nanomaterial itself makes it difficult to disperse in the coating and cause agglomeration,which in turn reduces the corrosion resistance of the resin.In this paper,molybdenum disulfide nanosheets with excellent corrosion resistance and mechanical properties are used as nanomaterials.In order to give full play to the role of nanomaterials and improve the properties of coatings,different methods were used to functionally modify them and obtain the excellent anti-corrosion epoxy composite coating.The specific research content and conclusions of this paper includes the following parts:(1)On the surface of the molybdenum disulfide nanosheets,only the silane coupling agent KH560 was introduced into the small molecule epoxy group to improve its dispersibility and the interfacial bonding between the nanomaterial and the resin.Through various characterization tests,it was proved that KH560 has been successfully grafted and coated on the surface of MoS2.At the same time,the effect of the amount of modified material added on the corrosion resistance of the epoxy composite coating was studied.It was found that the KH560-MoS2/EP composite coating has higher EIS resistance than the MoS2/EP or pure epoxy resin coating,and the effect of high temperature and high pressure and salt spray test is better,especially when the additive amount is 0.8wt.%obviously.The self-corrosion potential of the 0.8wt.%composite coating was-0.42,which was lower than that of other added composite coatings,however,after soaking in 3.5wt.%NaCl solution for 168h,it also entered the late stage of soaking.After the high-temperature and high-pressure tests,there was no bubble on the surface of the coating and good adhesion was still maintained.No coating was peeled off at the scratches.After the salt spray test,there was no rust on the surface of the steel sheet and the adhesion was good.(2)MoS2 was coated by dopamine self-polymerization to increase the functional group on the surface of molybdenum disulfide and improve its dispersibility.MoS2 was coated by dopamine self-polymerization to increase the functional groups on the surface of molybdenum disulfide and improve its dispersibility.Small-molecule epoxy groups were then introduced to obtain KH560-PDA-MoS2,which was characterized by XRD and other tests in order to prove the successful modification of MoS2.Epoxy composite coatings were prepared by the blending method.The influence of the amount of modified materials on the corrosion resistance of the coatings was also studied.The results show that the corrosion resistance of KH560-PDA-MoS2/EP composite coating is better than that of pure epoxy resin.The composite coating is in the middle of soaking after immersed in the corrosive medium for 168 h,and it keeps higher impedance value.The addition of 0.8%by weight of the modified material KH560-PDA-MoS2 to the resin matrix improves the corrosion resistance more than other amounts.From the polarization curve,it can be seen that the current density or self-corrosion potential of the composite coating under this addition is the lowest,and the EIS results at various soaking stages show the best corrosion resistance.(3)MoS2 nanosheets encapsulated with PDA were used as the support template,and ZrOCl2·8H2O was added in an appropriate proportion.The ZrO2 particles were uniformly grown on the surface of MoS2 by hydrothermal method,and epoxy groups were grafted to prepare KH560-ZrO2-PDA-MoS2 hybrid material.The characterization tests demonstrated that the KH560-ZrO2-PDA-MoS2 hybrid material was successfully prepared and when the molar ratio of ZrOCl2·8H2O to MoS2 was 1.2:1,the Zr02 nanoparticles could uniformly adhere to the MoS2.The corrosion resistance of KH560-ZrO2-PDA-MoS2/EP composite coating shows that the addition of this modified filler has the most significant effect on the corrosion resistance of the coating.The EIS test,the high temperature and high pressure test,and the salt spray test result are higher than the previous two.All kinds of materials are good,and the best amount of filler is 0.8wt.%. |
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