I'm not sure that welding is the best method. With soldering you're not heating the cable enough to change the composition of the metal so much. Raising the heat to the welding stage lets things move around and exposes corrodible bits to the elements. To properly weld stainless you need to passivate the surface afterwards so it doesn't corrode. I'm not a metallurgist but I know enough about it that there's more to it than simply welding stainless and it staying stain less