Study On Hydrogen Permeation Behavior Of P110 Steel In H 2 S/CO 2 Environment

H2S/CO2 corrosion has been one of the biggest problems to restrict the exploitation of oil and gas. In H2S/CO2 environment, hydrogen ions are reduced to hydrogen atoms on the surface of steels. The possibility of the hydrogen induced cracking (HIC) is increased owing to the introduction of H2 into the steels. The behavior of HIC is related to the diffusion rate and mechanism of hydrogen permeation process. P110 tubing steel is a commonly used in oil and gas field. Therefore, the research on hydrogen permeation process of P110 steel in H2S/CO2 environment is significant for safe exploration in oil and gas industry.The electrochemical and hydrogen permeation behaviors were studied by electrochemical and Devanathan-Stachurski double cell methods. Experimental results showed that the number of irreversible hydrogen trapping was less than reversible hydrogen trapping. The permeation time of hydrogen diffusion was only effected by irreversible hydrogen trapping. However, the hydrogen diffusion coefficient was sharply influenced by the reversible hydrogen trapping. The electrochemical behavior of P110 steel after hydrogen charging and the corresponding scanning electron microscopy (SEM) image were studied, the results showed that hydrogen charging can accelerate the possibility of HIC.The effect of CO2 and H2S concentration on the electrochemical and hydrogen permeation behaviors of P110 steel were investigated separately. The results showed that the corrosion current density was enhanced, while the polarization resistance and charge-transfer resistance decreased as the concentration of CO2 and H2S increased. The variation rule of hydrogen permeation behaviors can be described below:the hydrogen diffusion coefficient displayed little changed, while both of the diffusible hydrogen concentration and the steady-state hydrogen permeation current density increased. Also the steady-state hydrogen permeation current density in H2S environment was far greater than that in CO2 environment, which was caused by the toxification of H2S. The relation of the hydrogen diffusion coefficient and temperature can be described by Arrhenius equation through fitting the hydrogen permeation curves at different temperatures.FeCO3 and FeS1-x corrosion films were prepared respectively on the surface of P110 steel in CO2 and H2S dissolved distilled water. Also the phases and microstructures of corrosion films were analyzed by X-ray diffraction (XRD) and SEM. The electrochemical performance of the above films were tested by the methods of electrochemistry. The influence of the films on hydrogen permeation process were investigated by hydrogen permeation testing. The results showed that FeCO3 film can inhibit the corrosion of steel effectively. Moreover the semiconductor type of films changed from p-type to n-type. However, the FeS1-x film showed a poor anti-corrosion ability and presented p-type semiconductor. While the results of hydrogen permeation testing indicated that hydrogen permeation current density and the hydrogen diffusion coefficient of both films greatly decreased, which was caused that the superficial hydrogen adsorption concentration was effected and the diffusion of hydrogen was hindered into the base metal by the films.