I've seen many welders sand the copper coating from the filler rods before they will weld. I've never done this. I can't see where it makes any difference, but maybe I don't have the experiance to see the difference.
They all swear by it, and would never weld without first sanding the copper off. Anyone with a real answer? Oh and what about my 308 rods? I see people sanding those too. I hope I'm not opening a can of worms..