CORROSION ASSESSMENT OF THE AA5754 PLASMA-MIG WELDING

Abstract

The microstructure of the automotive aluminium wrought alloys can be significantly modified by the high heat input employed during fusion welding techniques, such as the plasma metal inert gas (MIG)welding. Plasma-MIG welding of the AA5754 alloy using silicon-rich filler wire (AA4043A) results in the formation of a partially melted zone (PMZ) adjacent to the fusion boundaries. Partial melting of the Al-Fe-Mn-(Si) intermetallics at the partially melted zone, and segregation of the high melting point elements (particularly Fe and Mn) towards the fusion zone increase the open circuit potential difference between the weld and its adjacent partially melted zones. Consequently, severe galvanic corrosion attacks take place preferentially along the PMZ at each side of AA5754 weld during exposure to aqueous corrosion environments.