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<p>Al<sub>2</sub>Sn precipitates in Al-Sn bearing alloys are susceptible to inducing localized micro-galvanic corrosion, but the underlying physicochemical mechanisms and interfacial electronic origins remain insufficiently understood. In this study, the pitting behavior associated with Al<sub>2</sub>Sn precipitates was investigated by combining multiscale characterization, electrochemical measurements, and first-principles calculations based on density functional theory. The investigated Al-Sn alloys are practically relevant to cast bearing components, including automotive engine bearing bushes, marine sliding bearings, and heavy-duty machinery bushings, where castability, conformability, and corrosion resistance must be simultaneously considered. The results show that the size and distribution of Al<sub>2</sub>Sn precipitates strongly affect pitting susceptibility. A Sn content of 7.0&#xa0;wt.% combined with solution treatment, water quenching, and aging produces a relatively fine and dispersed distribution of Al<sub>2</sub>Sn precipitates, leading to an increased charge transfer resistance and reduced pitting tendency while retaining Sn-rich soft phases required for bearing applications. XPS and SEM/EDS analyses indicate that pitting is governed by an Al<sub>2</sub>Sn-cathode-dominated micro-galvanic process coupled with autocatalytic occluded cell evolution. The volumetric mismatch between in situ formed SnO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> may generate localized stresses that promote passive film rupture near phase boundaries. First-principles calculations reveal a work function-derived potential difference of approximately 0.167&#xa0;V between Al<sub>2</sub>Sn(210) and Al(111), supporting the tendency of Al<sub>2</sub>Sn to act as a micro-cathodic phase. Furthermore, the calculated orbital mismatch and charge localization at the Al/Al<sub>2</sub>Sn interface suggest enhanced interfacial reactivity, which may promote chloride-induced passive film breakdown. This study provides mechanistic insight into the micro-galvanic corrosion of cast Al-Sn bearing alloys and offers qualitative guidance for composition design and heat treatment optimization of corrosion-resistant bearing components.</p>

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A Combined Experimental and First-principles Study on the Micro-galvanic Corrosion Mechanism Induced by Al2Sn Precipitates in Al-Sn Bearing Alloy

  • 期刊论文

  • 发表日期：

    2026年7月20日

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  • Haitao Yang,
  • Lianbao Yang,
  • He Wei,
  • Qing Li,
  • Xiangming Li

摘要

Al2Sn precipitates in Al-Sn bearing alloys are susceptible to inducing localized micro-galvanic corrosion, but the underlying physicochemical mechanisms and interfacial electronic origins remain insufficiently understood. In this study, the pitting behavior associated with Al2Sn precipitates was investigated by combining multiscale characterization, electrochemical measurements, and first-principles calculations based on density functional theory. The investigated Al-Sn alloys are practically relevant to cast bearing components, including automotive engine bearing bushes, marine sliding bearings, and heavy-duty machinery bushings, where castability, conformability, and corrosion resistance must be simultaneously considered. The results show that the size and distribution of Al2Sn precipitates strongly affect pitting susceptibility. A Sn content of 7.0 wt.% combined with solution treatment, water quenching, and aging produces a relatively fine and dispersed distribution of Al2Sn precipitates, leading to an increased charge transfer resistance and reduced pitting tendency while retaining Sn-rich soft phases required for bearing applications. XPS and SEM/EDS analyses indicate that pitting is governed by an Al2Sn-cathode-dominated micro-galvanic process coupled with autocatalytic occluded cell evolution. The volumetric mismatch between in situ formed SnO2 and Al2O3 may generate localized stresses that promote passive film rupture near phase boundaries. First-principles calculations reveal a work function-derived potential difference of approximately 0.167 V between Al2Sn(210) and Al(111), supporting the tendency of Al2Sn to act as a micro-cathodic phase. Furthermore, the calculated orbital mismatch and charge localization at the Al/Al2Sn interface suggest enhanced interfacial reactivity, which may promote chloride-induced passive film breakdown. This study provides mechanistic insight into the micro-galvanic corrosion of cast Al-Sn bearing alloys and offers qualitative guidance for composition design and heat treatment optimization of corrosion-resistant bearing components.