Study On Corrosion Behavior Of Super13Cr Stainless Steel Tubing In Mud Acid

The corrosion behavior of super13Cr martensitic stainless steel in mud acid is studiedby the simulation corrosion test of fresh acid and subsequent conditions combine withelectrochemical analysis test and SEM, confocal laser scanning, XPS and XRD methods. Theresults show that:Inhibition of corrosion inhibitor for super13Cr martensitic stainless steel in fresh acid(mud acid) at the rage of60℃-160℃is in the primary standard criteria, with temperatureincreased, the average corrosion rate, maximum pit depth, average corrosion depth and theaverage corrosion rate are all increased. Although the uniform corrosion rate of super13Crmartensitic stainless steel in fresh acid is up to14.5516mm/a, uniform corrosion rate is farless than the required standard of oil and gas field that can be accepted. Therefore, in the viewof uniform corrosion rate of super13Cr martensitic stainless steel, there is a excellentmatching between corrosion inhibitor and super13Cr martensitic stainless steel.Electrochemical properties of the super13Cr martensitic stainless steel in differenttemperature fresh acid solution is studied by electrochemical analysis.Results show thatreaction rate of H+in the cathodic is increased as temperature increasing, which causescorrosion potential is increased;the corrosion inhibitor decreases corrosion current densityby the way of inhibiting cathodic and anodic reaction, corrosion inhibition efficiency canreach above90%that shows a good corrosion inhibition performance;the inhibitor cansignificantly improve the Tafel slope of cathodic and anodic and can inhibit cathodic andanodic reaction, so the type of the corrosion inhibitor is a mixed control of anode reactioninhibitor.Super13Cr martensitic stainless steel with a very high corrosion rate in the corrosionconditions of fresh acid，in contrast, uniform corrosion of super13Cr martensitic stainlesssteel under the condition of the acid residue and conditions of CO2corrosion is mild,corrosion rate is low, thus, in terms of uniform corrosion severity, corrosion of fresh acid isthe most serious in the conditions of corrosion simulation test.Super13Cr martensitic stainless steel with120℃fresh acid-120℃and170℃residualacid-120℃and170℃CO2corrosion of formation water, pitting density increased significantly, compared to the phenomenon of obvious pitting in the independent residualacidcorrosion and CO2corrosion of independent formation water is not appeared, the reason maybe due to the formation of the adsorption film (or corrosion product film) in the process offresh acid corrosion is incomplete coverage in the process of residual acid corrosion andconditions of CO2corrosion, which promotes the initiation of pitting corrosion.