Study On Corrosion Behavior Of X70 Steel Under The Synergistic Action Of Direct Current And SRB

With the development of power grids and oil and gas pipeline networks,the spatial distance between the two is gradually decreasing,and inevitably,intersections will occur in some areas.The direct current environment of these public spaces and the microorganisms in the soil will definitely change significantly compared with the single factor,and the corrosion problem will be more complicated.Therefore,this paper uses a self-made experimental device to build a corrosive environment under the action of direct current and SRB.Electrochemical methods combined with SEM and EDS microanalytical methods were used to study the influence of direct current and SRB on the corrosion behavior of X70 pipeline steel in near-neutral pH soil simulated solution.The main conclusions of this paper are as follows:(1)When the applied DC electric field intensity is low(less than 200 V/m),the SRB growth is basically unaffected;when the electric field strength is 500 V/m,the efficiency of the material transfer inside and outside the SRB cell membrane and the metabolic activity of the bacteria are gradually enhanced;At 1000 V/m and 1500 V/m,the electric field changes the permeability of the microbial membrane,resulting in the inactivation of SRB cells and accelerating the death of SRB in NS4 solution.(2)Under the action of DC electric field,the degree of corrosion of X70 steel in sterile NS4 solution is aggravated with the increase of applied field strength or the increase of action time.When SRB and DC electric field work together,when the DC electric field strength is low(less than 500 V/m),SRB can form a protective microorganism film.The corrosion rate of X70 steel is the lowest with the increase of field strength;When the electric field strength increases above 1000 V/m,the SRB growth is inhibited.At this time,the corrosion behavior of X70 steel is mainly controlled by the electric field,and the corrosion of the sample increases with the increase of the field strength.(3)When the applied DC current density reaches 0.1 mA/cm2,the decay phase of SRB in near-neutral soil is advanced to 7d.When the applied current continues to increase above 0.5 mA/cm2,the logarithmic growth phase of SRB is shortened to 1-3 d,the decay phase is advanced to the 5th day,and the death phase is advanced to the 9th day.(4)The corrosion rate of X70 steel in the sterile NS4 solution increases with the increase of the applied DC current density or the increase of the action time.When SRB and DC current work together,when the applied DC current density is low(0.1 mA/cm2),the microbial and corrosion product layers are gradually thickened and dense,which reduces the corrosion rate of X70 steel;When the current density continues to increase,the corrosion product cracking,can not effectively protect the metal matrix,the corrosion of X70 steel is intensified.