Hey, I have lurked here for a while and been able to search for most of my answers, but finally have a question. I picked up a 50# argon/co2 (90/10) tank on the cheap in the hopes that I could trade it in on a co2 tank. None of the welding shops around here are wanting to exchange it, they're wanting me to take it to the shop on the sticker to see if they can exchange it.

I called them up, they asked if I had a title, of course I don't. They said bring it in and they'd see what they could do. A buddy of mine told me that tanks this large are probably leased and what they might do is confiscate it and that'll be that. He suggested taking the tag off and that I might get a welding supply shop to fill it with co2 for me.

Can co2 even be put into an argon tank? Aren't the valves and regulators different?