Aluminum Welding Guide

Alcoa research engineers discovered that stress corrosion cracking (SCC) in 5xxx series alloys can be encountered when used in elevated temperature applications. The research and resultant field performance data shows that 5xxx series alloys with magnesium contents above 3% are susceptible to SCC when exposed to prolonged temperatures between 150 and 350 degrees F. With prolonged exposure to these temperatures, precipitates can form in the grain boundaries that are highly anodic to the aluminum-magnesium matrix. It is this continuous grain boundary network of precipitates that produces susceptibility to stress corrosion cracking (SCC) and the potential for premature component failure.

Base metal 5454 was specifically developed by Alcoa for good strength and ductility characteristics when used in elevated temperature applications. Filler metal ER5554 was developed to weld base metal 5454 and both alloys contain magnesium contents between 2.4% and 3.0%. Therefore, both alloys are suitable for elevated temperature applications and are not susceptible to SCC.

Filler metal ER4043 does not have magnesium added to its alloy composition and can be used to weld 5xxx series alloys with up to 2.5% magnesium (nominal) as well as other base metals suitable for elevated temperature applications such as the 1xxx, 3xxx and 6xxx base metals.