If you are welding mild steel with zinc coating (eg shopping trolley) what are the pros and cons of using stainless steel MIG wire as opposed to mild steel MIG wire?
You'd want to remove the zinc before welding to avoid the nasty galv fumes and weld contamination. From there if it's a mild steel trolley use mild steel wire. The idea is to end up with much the same metal composition in the weld as in the surrounding area.