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Corrosion resistance of extruded Mg–3Al–1Zn alloy manufactured by adding CaO for the replacement of the protective gases
Author(s) -
Nam T.H.,
Kim S.H.,
Kim J.G.,
Kim S.K.
Publication year - 2014
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201206849
Subject(s) - corrosion , materials science , alloy , metallurgy
The corrosion properties were investigated for extruded Mg–3Al–1Zn (AZ31) alloy in alkaline NaCl solution which was manufactured by adding 0.5 wt% CaO without SF 6 protective gas. The results of electrochemical tests showed that the addition of 0.5 wt% CaO drastically increased the pitting potential and charge transfer resistance of the specimen, indicating that CaO addition enhances the film stability of AZ31 alloy. As results of electron probe X‐ray microanalysis (EPMA), Al 2 Ca phase and CaO was observed on the CaO‐added specimen. The Al 2 Ca phase was precipitated by the reduction of CaO, and was known as an effective corrosion barrier and hinders the corrosion propagation. Also, the CaO raw particle was observed, and could be remained after reduction as Al 2 Ca phase. Meanwhile, the Mg 17 Al 12 phase was not recognized due to the low content of Al in the AZ31 Mg alloy. The results of X‐ray diffraction (XRD) showed that Ca(OH) 2 and Al 2 Ca phase was observed on the CaO‐added AZ31 Mg alloy after immersion for 5 days, which increased the protectiveness of Mg(OH) 2 film of the CaO‐added specimen.