Time-sequential corrosion behaviour observation of micro-alloyed Mg-0.5Zn-0.2Ca alloy via a quasi-in situ approach. (September 2019)

• Record Type: Journal Article
• Authors: Jin, Yiming; Blawert, Carsten; Feyerabend, Frank; Bohlen, Jan; Silva Campos, Maria; Gavras, Sarkis; Wiese, Björn; Mei, Di; Deng, Min; Yang, Hong; Willumeit-Römer, Regine
• Is Part Of: Corrosion science. Volume 158(2019)
• Publication Date: 2019-09
• Subjects: A. Magnesium -- A. Alloy -- A. Intermetallics -- B. SEM -- B. TEM -- C. Anodic dissolution; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2019.108096
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: The effect of minor Si inclusion on the microstructure and corrosion performance of Mg-Zn-Ca alloy are discussed. Concern about chromic acid cleaning on Mg-Zn-Ca alloy is raised and a harm-free mechanical exfoliation method is proposed. Mg2 Ca phase is anodic and preferentially corrodes compared to the Mg matrix within the first hour of immersion. Ca2 Mg6 Zn3 and MgCaSi phases continuously act as cathodes until 24 h immersion. Abstract: The corrosion behaviour of as-cast and solution-annealed Mg-0.5Zn-0.2Ca alloy containing 150 ppm Si was investigated in 0.9% NaCl solution. The main secondary phases in the as-cast state are isolated MgCaSi and a coexisting intermetallic particle which consists of Mg2 Ca and Ca2 Mg6 Zn3 . A quasi-in situ approach is applied to investigate the corrosion initiation and development. It is proved that Mg2 Ca phase is anodic and preferentially corrodes within the first hour of immersion. Whereas, Ca2 Mg6 Zn3 and MgCaSi phases continuously act as cathodes until 24 h. After solution annealing, the more homogeneous microstructure and reduced galvanic corrosion result in a higher corrosion resistance.