Influence of Service Temperature On the Resistance of Wrought Aluminum-Magnesium Alloys to Corrosion

The wrought aluminum-magnesium alloys are being used in many welded structural applications; however, the alloys of higher magnesium content are not recommended for service where the operating temperature exceeds about 150 F. The reason for this limitation is that prolonged heating in the temperature range of 150 to 350 F causes selective precipitation of an anodic phase resulting in susceptibility to intergranular corrosion, and in the presence of a high enduring tensile stress, causes stress-corrosion cracking.This paper presents extensive data on the effect of continuous heating on the metallurgical structure and resistance of these alloys to stress-corrosion cracking. It further describes a new alloy, 5454, which is shown to be free from the temperature limitation placed on the higher magnesium alloys. 6.4.2