The objective of this article is to provide an overview of the main welding defects that frequently exist in piping and equipment and how to detect these defects without destroying the welds using non destructive testing (NDT) methods. Then, the sensitization of stainless steel weld, characterization, processing, and structure properties of Heat Affected Zone (HAZ) as well as weld metal will be discussed in detail. Furthermore, this article will illustrate the treatment of the weld decay by recovery of passivation film after welding which will be followed by prevention of intergranular corrosion or weld decay of stainless steel using surface mechanical attrition treatment and all of these will be described with help of characterization techniques XRD, SEM, TEM, and EPMA.