A corrosion study of nickel-copper and nickel-copper-palladium welding filler metals

In an effort to reduce the release of fumes containing carcinogenic Cr6+ during arc welding of stainless steel, Cr-free filler metals for welding of SS304 have been developed. Corrosion studies were carried out on 304L stainless steel samples welded with these Cr-free consumables. The corrosion properties of gas tungsten arc (GTA) and shielded metal arc (SMA) welds fabricated with Ni-Cu and Ni-Cu-Pd consumables were found to be comparable to those of welds fabricated with SS308L, the standard filler metal used with SS304. Although the breakdown potentials of the welds made using both welding processes were lower than that of the SS308L GTA weld, the repassivation potentials of these welds were much higher. Generally, the repassivation potential is a more conservative measure of susceptibility to localized corrosion. Accordingly, the Ni-Cu and Ni-Cu-Pd welds were more resistant to crevice corrosion than SS308L welds. The addition of a small amount of Pd improved the corrosion resistance relative to Ni-Cu welds, which is consistent with previous studies from specially-prepared button samples and bead-on-plate samples. Other corrosion studies such as creviced and uncreviced long time immersion, atmospheric exposure, and slow strain rate testing suggest that Ni-Cu-Pd filler metal can be a potential replacement for the conventional SS308L filler metal for joining SS304.