J. Mater. Sci. Technol. ›› 2017, Vol. 33 ›› Issue (9): 954-960.DOI: 10.1016/j.jmst.2017.01.014

Special Issue: 2017腐蚀与防护专辑 2017-2018年Mg合金专题

• Orginal Article • Previous Articles     Next Articles

Pitting corrosion of a Rare Earth Mg alloy GW93

Song Yingwei*(), Shan Dayong, Han En-Hou   

  1. Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
  • Received:2016-10-24 Revised:2016-11-28 Accepted:2016-12-21 Online:2017-09-20 Published:2017-10-16
  • Contact: Song Yingwei
  • About author:

    1 The authors contributed equally to this work.

Abstract:

Pitting corrosion of magnesium (Mg) alloys is greatly associated with their microstructure, especially second phases. The second phases in traditional Mg alloys such as AZ91 are electrochemically nobler than Mg matrix, while the second phases in Rare earth (RE) Mg alloy GW93 are more active than Mg matrix. As a result, the pitting corrosion mechanism of Mg alloy GW93 is different from the traditional ones. This paper aims to clarify the pitting corrosion mechanism of Mg alloy GW93 through the studies of Volta potential by Scanning Kelvin Probe Force Microscopy (SKPFM), corrosion morphology by Scanning Electron Microscope (SEM), and corrosion resistance by electrochemical tests. Results reveal that the pitting corrosion of GW93 includes three stages, first, dissolution of the second phases, followed by corrosion of Mg matrix adjacent to the dissolved second phases, and finally, propagation of corrosion pits along the depth direction of the dissolved second phases. Anodic second phases and enrichment of Cl- in the thick corrosion product films dominate the propagation of pitting corrosion.

Key words: Mg alloys, Pitting corrosion, Second phases, Oxide films