Synergetic effect of Mg2Si and Si particles on intergranular corrosion of Al-Mg-Si alloys through multi-electrode coupling system

Chaoxing Li, Jinfeng Li, Nick Birbilis, Zhiqiang Jia, Ziqiao Zheng

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Abstract

The potentiodynamic scanning curves and the electrochemical coupling behaviors of constituent phases at the grain boundary of Al-Mg-Si alloy were investigated. The corrosion mechanism of Al-Mg-Si alloys different ratio of Mg to Si was analyzed. The results show that the Si particle is cathodic to the Al-base and causes the anodic dissolution of Al-base at its adjacent periphery. At the beginning, the precipitate of Mg2Si is anodic to the Al-base and corrosion occurs on its surface. However, during its corrosion process, its potential moves to a positive direction with immersion time increasing, due to the preferential dissolution of Mg and the enrichment of Si, which makes Mg2Si become cathodic to Al-base and leads to the anodic dissolution of the Al-base at its adjacent periphery at a later stage. At the grain boundary of Al-Mg-Si alloys with a ratio of Mg to Si higher than 1.73, the Mg-and-Si contained precipitates are distributed discontinuously, resulting in that they are not sensitive to intergranular corrosion. There exist Mg-and-Si-contained precipitates and Si particles at the grain boundary of Al-Mg-Si alloys with a ratio of Mg to Si less than 1.73, corrosion occurs firstly on the surface of Mg2Si. Meanwhile, the Si particle leads to the great anodic dissolution of the precipitate-free-zone(PFZ) at its adjacent periphery. The Si particle also accelerates the preferential dissolution of Mg in Mg2Si precipitate, expediting the polarity transformation between Mg2Si and the PFZ. As a result, the corrosion development along the PFZ at the adjacent of Mg2Si particle is enhanced.

Original languageEnglish
Pages (from-to)107-113
Number of pages7
JournalJournal of the Chinese Society of Corrosion and Protection
Volume30
Issue number2
Publication statusPublished - 11 Oct 2010

Keywords

  • Al-mg-si alloys
  • Corrosion mechanism
  • Intergranular corrosion

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