Corrosion of innovative magnesium Mg alloys

Abstract This chapter deals with the corrosion performance of innovative or unconventional magnesium (Mg) alloys. It considers, on the one hand, all Mg alloys that have an unusual microstructure and/or composition mostly as a result of extreme processing conditions and, on the other hand, the innovative concepts that are used to improve the corrosion performance of conventional alloys. The available literature is reviewed and the specific influences of the microstructure and/or composition on corrosion behaviour is discussed and general possibilities to improve corrosion resistance of these alloys are highlighted. 

Key words recycling alloys, amorphous alloys, alloy coatings, laser surfacing, laser alloying. 

However, the development of secondary Mg alloys requires a completely different concept compared with standard alloys, which obtain their corrosion resistance by reducing the levels of impurities below certain alloy-specific and process-dependent limits. Although control of impurities is technically possible, this would make the secondary alloys too expensive. A cheaper 

2 Comparison of the galvanic current measured between either B or X and pure magnesium in 5% NaCl solution (pH 11). 

In spite of good castability, strength and corrosion behaviour of the AZC1231 secondary alloy, suggesting that this alloy may be a suitable alternative for many applications, it cannot be used in places where ductility is important. For wrought processing or more ductile cast applications an additional secondary Mg alloy group is required. 

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Since the corrosion performance of a metal is determined primarily by its chemical composition and microstructure, an understanding of the metallurgical effects on corrosion is critically essential. Part II considers the role of typical microstructures and alloying elements of Mg alloys in corrosion. Metallic glass Mg alloys and some other innovative magnesium alloys are also discussed for their interesting atypical compositions or microstructures. This part provides an extension and development of the fundamentals presented in Part I. 

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