You are correct. It has to be CLEAN and wire brushed with stainless steel really good other wise you'll want to kill yourself. I've only ever TIG welded aluminum. I did some that was dirty and I couldn't get it to do anything but burn holes. I've done a few on new clean aluminum and it was much easier, haha.
Making something like that air tight is a pain. Just about everywhere you start/stop you'll have a pin hole and sometimes it's a pain to seal that little hole.
Still looks good though :thumb:. Make me want to weld some aluminum again.
Yellowchevy