ya, you CAN, but weldin thicker metal to a thinner base metal makes it more difficult to determine how much heat is going into the thinner base metal, there fore its easier to blow through....n once that happens, you'll put a ton of heat into the thin metal...its just a mess...so dont be dumb, do it right the first time, cuz if ya screw it up n have to grind it off, then the metal is weakened and its now worthless to weld to it and expect it not to break... learned that in metallury...