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<p>The precipitation behavior, corrosion, and passivation performance of solutionized and severely sensitized SAF 2507 super-duplex stainless steel subjected to a temperature of 900&#xa0;°C for 10&#xa0;h are investigated in a twofold concentrated seawater at 60&#xa0;°C. The sensitized alloy exhibits 66.1% γ phases and 33.9% σ phases, and the original α phases have completely decomposed through eutectoid transformation, resulting in a microstructure characterized by coarse blocky σ/γ<sub>2</sub> aggregates. High defect densities and an increased amount of oxyhydroxides and hydroxides are present in the passive film on the sensitized alloy, thereby enhancing n-type semiconducting character. The inferior performance of the passive film on the sensitized alloy is ascribed to the increased potential drop across the film/solution interface, the high defect densities, and the pronounced n-type character of the passive film resulting from the variations in its constituents. The precipitation of σ phase during sensitization significantly increases intergranular corrosion susceptibility and decreases critical pitting temperature, breakdown potential, and polarization resistance in hot concentrated seawater.</p>

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Corrosion and passivation behavior of sensitized SAF 2507 super-duplex stainless steel in hot concentrated seawater

  • 期刊论文

  • 发表日期：

    2025年5月31日

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  • Wen-bin Gao,
  • Yi Gu,
  • Qing-lin Han,
  • Xiao-yan Gu,
  • Wei Guan,
  • Sheng-bin Zhao,
  • Wen-hang Li

摘要

The precipitation behavior, corrosion, and passivation performance of solutionized and severely sensitized SAF 2507 super-duplex stainless steel subjected to a temperature of 900 °C for 10 h are investigated in a twofold concentrated seawater at 60 °C. The sensitized alloy exhibits 66.1% γ phases and 33.9% σ phases, and the original α phases have completely decomposed through eutectoid transformation, resulting in a microstructure characterized by coarse blocky σ/γ2 aggregates. High defect densities and an increased amount of oxyhydroxides and hydroxides are present in the passive film on the sensitized alloy, thereby enhancing n-type semiconducting character. The inferior performance of the passive film on the sensitized alloy is ascribed to the increased potential drop across the film/solution interface, the high defect densities, and the pronounced n-type character of the passive film resulting from the variations in its constituents. The precipitation of σ phase during sensitization significantly increases intergranular corrosion susceptibility and decreases critical pitting temperature, breakdown potential, and polarization resistance in hot concentrated seawater.