The current study articulates the influence of filler metal on the pitting and intergranular corrosion susceptibility of gas tungsten arc welded (GTAW) 316L stainless steel weldments made with 308L, 304L and 316L filler materials.

The open circuit potential (OCP), potentio-dynamic polarisation (PDP), and double loop electro-chemical potentio-kinetic re-activation (DL-EPR) techniques were used to evaluate the corrosion behaviour of 316L GTA weldments in a 3.5% NaCl electrolyte solution at three distinct regions, namely the parent metal (PM), heat affected zone (HAZ), and fusion zone (FZ).

From the electrochemical studies, it is found that welds made with 316L filler metal show a relatively higher pitting potential and a lower degree of sensitization (%DOS) when compared to the parent metal and welds made with 304L and 308L fillers. It is related to the presence of molybdenum, which stabilizes the passive layer against aggressive Cl- ions, and also chromium and nickel elements, which are favourable for enhanced corrosion resistance.

The IGC susceptibility of all 316L weldments were tested in a 10% oxalic acid etch test in accordance with ASTM 262 practice A. It is observed that severe IGC attack was found in the HAZ region of all weldments and was more in 304L filler followed by 308L and 316L filler materials.

This could be attributed to the presence of a lower temperature gradient, which increases in the depletion of chromium through the formation of chromium carbide at grain boundaries.

This article is shared by Surjan Sheik , Atmaramudu Tirumalla and Raffi Mohammed from Department of Metallurgical and Materials Engineering, National Institute of Technology, Andhra Pradesh.