Study On Crevice Corrosion Of Super 13Cr In Simulated Oil And Gas Field Environment

Based on the method of simulating occluded cells,this paper does a research on the critical pH value and its influencing factors in the crevice corrosion environment by means of electrochemical equipment and other laboratory equipments;what's more,this paper further studies the super 13Cr under different working conditions by simulating the corrosion environment of oil and gas fields;this thesis studies the electrochemical behavior of the passivation film on the surface of the super 13Cr and the corrosion product film under the condition of crevice corrosion by polarization curves and AC impedance spectra.Research indicates:(1)The pH value in the occlusion zone decreases with the prolongation of the polarization time,and eventually stabilizes,ie,there is a critical pH value in the gap;in the same occlusion system,the polarization current density and temperature have little effect on the critical pH value.However,as the polarization current density and temperature increase respectively,the time for the solution to reach the critical pH in the gap decreases;(2)The degree of occlusion is of great influence on the critical pH value in the gap.With the increasing degree of occlusion,the critical pH value decreases and the degree of corrosion is relatively serious.(3)In the three different corrosion environments of simulated formation water,completion fluid and salt water,the crevice corrosion potential of super 13Cr decreases with the increase of temperature;the corrosion current density increases,crevice corrosion tends to become large,and the corrosion rate changes large;(4)In the environment of formation water corrosion,with the increase of salinity,the gap potential of Super 13Cr decreases,the corrosion current density increases,and the corrosion rate increases.(5)With the increase of pH in the medium,the corrosion current density and corrosion rate of Super 13Cr show a decreasing trend.(6)The crevice corrosion in this paper mainly occurs under conditions of anoxic or anoxic conditions.The initial stages are mainly:the cathode is mainly H~+,and H~+is reduced to H;and the anode is the dissolution of metal.At the later stage,the autocatalytic mechanism plays a leading role in accelerating the corrosion of metal within the gap.