Inert Gas Tungsten Arc Welding (GTAW) process is one of the most widely used welding processes in which material is prone to stress corrosion cracking (SCC). Stress corrosion indicates cracking due to combined effect of stress and corrosion. Many rupture incidents have occurred due to this type of cracks. Effect of ultrasonic waves were studied on GTAW welded SS316L metal, in this paper. Two samples were healed by post weld ultrasonic treatment, two samples by post weld heat treatment and two were considered as control samples with no post treatment. Residual stress of all six pieces were measured by XRD method. Afterwards, samples were placed in corrosion environment. Results show that residual stress was decreased to 54.3% using heat treatment whereby this decreased to 58.7% by ultrasonic waves. It was also shown that untreated samples cracked after 720 hours, while no crack was seen in post weld ultrasonic treated samples.