Corrosion Behavior of Pipeline Steel with Different Microstructures Under AC Interference in Acid Soil Simulation Soluti
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Corrosion Behavior of Pipeline Steel with Different Microstructures Under AC Interference in Acid Soil Simulation Solution M. Zhu, Y.F. Yuan, S.M. Yin, G.H. Yu, S.Y. Guo, Y.Z. Huang, and C.W. Du (Submitted August 16, 2018; in revised form January 15, 2019) Corrosion behavior of X65 pipeline steels with different microstructures under alternating current (AC) interference was investigated in acid soil simulation solution by potentiodynamic polarization curve, potentiostatic polarization curve and immersion test. The results show that superimposed AC causes a sharp increase in corrosion current density of X65 steel. With the increase in iAC, the corrosion current densities of steels with various microstructures increase, especially at high iAC. Hot-rolled steel mainly experiences uniform corrosion, with very slight pit corrosion. Serious corrosion degrees with intensive corrosion pits can be observed on the surfaces of normalized and quenched microstructure steels. The annealed steel exhibits the feature of non-uniform corrosion with some pitting. The steels with various microstructures applied with AC have different corrosion resistance. The normalized steel shows the worst corrosion resistance, then the quenched microstructure, and the hot-rolled steel displays the optimum corrosion resistance. The difference in the microstructure can result in difference in corrosion degree and occurrence position of pitting corrosion of X65 steel. The normalized microstructure composed of polygonal ferrite and a large amount of pearlite and bainite is the most susceptible to AC corrosion. Keywords
AC interference, microstructure, pipeline steel, pitting corrosion
1. Introduction With rapid development of electricity, energy and transportation industry, a growing number of buried steel pipelines are installed in proximity to overhead high-voltage AC power transmission lines or AC-powered rail transit systems due to the limited spaces to construct these facilities. In this case, AC corrosion is becoming the great threat to the safe operation of buried pipelines (Ref 1-3). Some research reports that the corrosion rate of pipeline steel is accelerated under AC interference (Ref 4-7). Xu (Ref 8) found that the corrosion of 16Mn pipeline steel is enhanced by the applied AC current density of 0-400 A/m2. Fu (Ref 9) reported that uniform corrosion occurs on the steel at a low AC current density, while a significant pitting corrosion is expected at a high AC current density. Song (Ref 10) reported that the corrosion rate of steel is affected by AC voltage, AC current density and AC frequency. Kuang (Ref 11) demonstrated that pitting corrosion could be initiated on the steel at sufficiently high AC current densities in both high pH and near-neutral pH solutions. Wang (Ref 12)
M. Zhu, Y.F. Yuan, S.M. Yin, G.H. Yu, and S.Y. Guo, School of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China; Y.Z. Huang, School of Materials Science and Engineering, Nanyang Technologi
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