Corrosion Protection of Joining Areas in Magnesium Die-Cast and Sheet Products

Abstract

The common joining techniques for Mg sheet and die cast alloys such as riveting, friction-stir welding and adhesive bonding all introduce additional challenges for protection in the joining areas. First of all, the sheet products are prone to high rate of corrosion due to surface contamination. Introduction of iron-rich contaminants can be encountered from the friction-stir welding process. Although powder coating on top of conversion pre-treatments is practical for mitigating corrosion, the lap-shear adhesion of such surfaces can be negatively impacted when the adhesively bonded joints are exposed to a corrosion environment. Anodized surfaces are better in terms of their ability to retain adhesion strength, but their resistance to galvanic corrosion is an issue. Development of galvanically compatible coatings for steel rivets will benefit the adaptation of riveting as a joining technology for magnesium.

Cold spray coatings to improve the corrosion resistance of magnesium (Mg) alloys

“…The protective capability of pure aluminum cold sprayed onto magnesium has also been demonstrated by others (McCune and Ricketts, 2004 ;Balani et al , 2005 ;G ä rtner et al , 2006 ;Zheng et al , 2006) ( Fig. 15.16 ).…”

Assessment of ageing effect on the mechanical behaviour of steel/aluminium self-piercing riveted joint

“…Galvanic corrosion of dissimilar metal joints will reduce joint strength if the joint is unprotected by a coating or by adhesive when subjected to a corrosive environment. A suitable procedure to enhance the corrosion resistance is to use organic or metallic coating to protect the metal substrate (Zheng et al 2007;Han and Chrysanthou 2008). González-García et al (2007) have investigated polyurethane polymeric film applied on metallic substrates; this coating showed higher adhesion and enhanced anticorrosion protection characteristics when applied on carbon steel rather than on galvanized steel.…”

Failure behaviour of SPR joints after salt spray test

“…A suitable procedure to enhance the corrosion resistance is to use organic or metallic coating to protect the metal substrate [31][32][33][34], i.e. a zinc metal coating could be used to enhance the corrosion resistance of rivet joints [35,36].…”