The Influence Of Tensile Stress On The Electrochemical Behavior Of X80Steel In A Simulated Acid Soil Solution

X80pipeline steel is widely used in the field of oil and gas transportation in21thcentury. The X80steel suffered stress corrosion in service under combined effect ofstress and corrosive environment. A lot of researches have been done about theinfluence of stress on corrosion behavior, but a basic consensus has not been concludedon its influence mechanism. Therefore, there is an obvious theoretical and practicalsignificance to study the influence of stress on electrochemical behavior of X80steel inacid soil environment.In this paper, the corrosion electrochemical behavior of tensile stress (0MPa、100MPa、200MPa、300MPa、400MPa) on the three microstructures of X80pipelinesteel were studied by electrochemical measurements. The sensitivity of threemicrostructures to stress as well as the influence rules of the electrochemical activityand the protectiveness of corrosion product film were also discussed. The mainconclusions are as follows:(1) The corrosion tendency increased when tensile stress applied on X80steel. Thewater quenching microstructure was most sensitive to stress, then the oil quenchingmicrostructure. Electrochemical impedance spectrum was composed of two and a halfarc for three different microstructures. As tensile stress increased, the reaction activityof the original microstructure of X80steel increased, the reaction resistance (Rct) valuebecame smaller by degrees, the corrosion product film resistance (Rf) firstly decreasedand then increased, and corrosion current densities changed conversely. The original ofwater quenching and oil quenching Rctdecreased and Rfincreased continually withincreasing stress.(2) The anodic dissolution occur preferentially at the “exposure” locations,resulting in a consequent promotion of corrosion activity and promoting theaccumulation of corrosion product on the one hand. On the other hand, tensile stressbroke corrosion product film, the protectiveness to matrix metal decreased; the waterquenching microstructure had eminent reaction activity due to high dislocation density,the oil quenching microstructure took second place, the minimum was originalmicrostructure.(3) As increased of tensile stress, the noise signal of original microstructure firstly decreased and then increased, the noise resistance changed conversely. The noise signalof water quenching microstructure increased with increasing stress, the noise resistancedecreased. The changed noise signal of oil quenching organization was consistent withthe water quenching samples.