Microstructure and pitting corrosion of partially melted zones of Al alloy GTA welds.

The corrosion behaviour of partially melted zones and heat affected zones of gas tungsten arc (GTA) welds in AA2219 and AA6061 alloys with different initial thermal tempers has been studied. Continuous and pulsed current GTA welding techniques were used. Potentiodynamic polarisation testing was carried out to determine the corrosion resistance. Optical and scanning electron microscopy studies were carried out to determine the corrosion mechanism. The partially melted zone of the welds was found to be attacked severely. A pulsing technique was found to decrease the severity of corrosion damage in the partially melted zone. The prior thermal temper of the alloys was found to influence the corrosion of heat affected zones of welds. [ABSTRACT FROM AUTHOR]