The Research Of Corrosion Behavior And Its Properties Of GFRP In CO₂Enviroment

Glass fiber reinforced plastic （GFRP） is widely used as pipes for gathering andtransportation of oil and gas by its excellent comprehensive properties. However,there are few research and related reports on the corrosion problems of GFRP pipes fortransport medium containing CO₂in oil and gas engineering. Therefore this study ofcorrosion behavior and its properties of GFRP pipes in CO₂medium enviromentalconditions is provided with significance.In this paper, aromatic amine curing and anhydride curing epoxy GFRP pipes aspipes were choosed for corrosion tests in medium containing crude oil, CO₂and waterin laboratory. The change in the functionl groups located in the inner surface of the twokinds of GFRP pipes before and after corrosion were analyzed by IR. The change in theelements and functionl groups of the two kinds of GFRP pipes before and aftercorrosion were analyzed by XPS. The change in the thermal effects and Tgof the twokinds of GFRP pipes before and after corrosion were analyzed by DTA. The change inmorphology of the surface and morphology of different delamination depth of the twokinds of GFRP pipes before and after corrosion were analyzed by SEM. The change inthe ring stiffness, barcol hardness, resin content, degree of curing, density and otherproperties of the two kinds of GFRP pipes before and after corrosion were analyzed. Bythe results of these analyses to explore chemical corrosion reactions and physicalcorrosion process of the two kinds of GFRP pipes in CO₂corrosion environment. Tostudy the influence of different pressures on the corrosion extent and physical andmechanical properties of the two kinds of GFRP pipes in CO₂corrosion environment.The results showed that the number of hydroxy （-OH） decreased and the number ofC-O-C increased of aromatic amine curing and anhydride curing epoxy GFRP pipes,and the number of carbonyl （C=O） of anhydride curing epoxy GFRP pipes decreasedslightly, but the change in the number of these functional groups were not large.Peviously, either of the two kinds of GFRP pipes suffered a chemical corrosion in theCO₂corrosion environment, but not serious. It is inferred that chemical corrosionmainly were CO₂with the hydroxy （-OH） of the surface of the pipes occured thechemical reaction, to produce the C-O-C at the same time also had water, and the part ofthe carbonyl （C=O） of the anhydride curing GFRP pipe occured the reaction too. TheSEM analysis showed that the two kinds of GFRP pipes suffered a physical corrosion inCO₂medium environment. The inner surface of the corroded pipes were rough, uneven,more defects appeared, the defects became lager, deeper, even micro-cracks appeared,the resin sheded and the fiber exposed out, and ring stiffness, barcol hardness, degree ofcuring, resin content, density and Tghad a certain degree of reduction. It is inferred that physical corrosion process mainly including the penetration and diffusion,“CO₂gasbomb” effect, the stress corrosion effect, fluid erosion effect. Pressure, as a veryimportant environmental factors, plays a role in accelerated the corrosion process. Thetwo kinds of GFRP pipes corrosion becomes more serious as the pressure increases, theproperties also reduced much more. So the pressure in the media environment should beto minimized when ensuring the normal engineering work in order to reduce thecorrosion rate.