We use carbon dioxide at work for ours migs. We use argon for Aluminum and tig. some different mixtures for spray and stainless. basic mig is pretty cool. for thick stuff i like the .045 outershield with carbon dioxide. the weld turns out pretty good and has a lot of penetration. you just have to break off the slag cover. we don't run arc at work and i haven't arc welded in over a year. not a fan of it. i have tig'd once and it takes some getting use too.
