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<p>To clarify the mechanism of corrosion perforation in carbon–steel exposed to low-temperature flue gas, we investigated a failed A106 Grade B pipe from a power plant in Xinjiang by macroscopic examination, metallography, scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy, together with an assessment of the service conditions. The chemical composition, microstructure and hardness all satisfied the relevant standards, excluding intrinsic material defects as the primary cause of failure. The perforation site was located in the boiler tail section adjacent to the heat-exchange fins, where air flowed inside the pipe and flue gas flowed outside. Large day–night temperature fluctuations promoted repeated formation and evaporation of a condensate film, so the inner wall underwent cyclic wet–dry corrosion and developed a mixed iron oxyhydroxide layer composed mainly of <i>α</i>-, <i>β</i>- and <i>γ</i>-FeOOH. Sulfur detected on the inner wall indicates that, after local penetration, sulfur-containing flue gas from the outer wall entered the inner wall through the perforation path, and the inner wall exhibited pronounced pitting corrosion. By contrast, the outer wall was dominated by oxidation and sulfidation and contained mainly FeOOH, Fe(OH)<sub>3</sub> and Na<sub>3</sub>Fe(SO<sub>4</sub>)<sub>3</sub>, consistent with overall uniform corrosion. The pipe therefore failed by severe perforation produced by the combined action of inner-wall pitting and outer-wall uniform corrosion.</p>

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Analysis of the Failure Mechanism of Corrosion Perforation of A106Gr.B Pipeline Steel in Low-temperature Flue-Gas Environment

  • 期刊论文

  • 发表日期：

    2026年8月5日

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  • Baojun Dong,
  • Zelin Ma,
  • Xiaokai Xing,
  • Guoyu An,
  • Guili Zhang,
  • Xin Yi

摘要

To clarify the mechanism of corrosion perforation in carbon–steel exposed to low-temperature flue gas, we investigated a failed A106 Grade B pipe from a power plant in Xinjiang by macroscopic examination, metallography, scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy, together with an assessment of the service conditions. The chemical composition, microstructure and hardness all satisfied the relevant standards, excluding intrinsic material defects as the primary cause of failure. The perforation site was located in the boiler tail section adjacent to the heat-exchange fins, where air flowed inside the pipe and flue gas flowed outside. Large day–night temperature fluctuations promoted repeated formation and evaporation of a condensate film, so the inner wall underwent cyclic wet–dry corrosion and developed a mixed iron oxyhydroxide layer composed mainly of α-, β- and γ-FeOOH. Sulfur detected on the inner wall indicates that, after local penetration, sulfur-containing flue gas from the outer wall entered the inner wall through the perforation path, and the inner wall exhibited pronounced pitting corrosion. By contrast, the outer wall was dominated by oxidation and sulfidation and contained mainly FeOOH, Fe(OH)3 and Na3Fe(SO4)3, consistent with overall uniform corrosion. The pipe therefore failed by severe perforation produced by the combined action of inner-wall pitting and outer-wall uniform corrosion.