Microstructure and pitting corrosion of partially melted zones of A356 Al-Si alloy welds

The corrosion behaviour of weld metal, partially melted zones and heat affected zones of gas tungsten arc welds in A356 Al-Si alloy with different prior thermal tempers has been studied. Continuous and pulsed current gas tungsten arc welding techniques were used. Potentiodynamic polarization 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 condition of the alloys was found to influence the corrosion of heat affected zones of welds.