Copper-Zinc Alloy

Copper-zinc alloys, i.e. brass, you don't weld like steel. The problem is that zinc evaporates quickly when heated. You see that from the white smoke, and it makes the weld porous and weakens the material. So you have to work with as little heat as possible and apply heat locally rather than broadly. Best suited for this is TIG welding with AC. Once the zinc burns off, adding filler won't help; the weld will still be bad. Let the workpiece cool slowly in air after welding, never quench with water, or you'll get cracks. And remember: the fumes are toxic, so extract them well or weld outdoors.