Cailiao Baohu (Nov 2023)

Analysis of Simulated Corrosion Behavior on the Inner Wall of Refined Oil X60 Steel Pipelines in Southwest China

  • CHEN Siya, ZHANG Chen, XIONG Daoying, WANG Yao

DOI
https://doi.org/10.16577/j.issn.1001-1560.2023.0278
Journal volume & issue
Vol. 56, no. 11
pp. 181 – 192

Abstract

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To explore the corrosion behavior on the inner wall of refined oil pipelines in gasoline and diesel, X60 steel samples were immersed for 7 d in a simulated service environment of refined oil pipelines in Southwest China. Laboratory research was conducted on the effects of mechanical impurities, water content and pipeline defects on the internal corrosion behavior of X60 pipeline steel using methods such as corrosion weight loss test, scanning electron microscope (SEM), 3D morphology characterization, stress-strain analysis, and open circuit potential (OCP). Results showed that the internal corrosion rate of the pipeline under conditions with mechanical impurity deposition was approximately seven times higher than that in deposition-free conditions. Furthermore, environments with mechanical impurities posed greater corrosion risks on pipeline than refined oil media. As water content increased from 0 to 1%, there was a corresponding acceleration in the corrosion rate, an increase in the incidence of pitting corrosion, the internal corrosion of the pipeline was mainly electrochemical corrosion accompanied by pitting corrosion caused by Cl-. The maximal corrosion rate of the base material observed in gasoline containing 1% (volume fraction) tap water was 0.047 mm/a. The analysis of pipeline defects showed that the existence of defects increased the corrosion rate of pipeline steel. The smooth dent was primarily characterized by stress corrosion. When the depth of the dent reached 9%, severe localized corrosion was observed at the center of the dent. With a water content of 1%, the corrosion rate was measured to be 0.075 2 mm/a. Welded joints were primarily characterized by galvanic corrosion, with localized corrosion and pitting being predominant, and the heat-affected zone (HAZ) exhibited a significant tendency for corrosion. When the water content was 1%, the corrosion rate was measured to be 0.080 35 mm/a.

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