Buying tanks reasonably cheaply can be done but you have to know a few things. First, you need to check with your local welding gas supplier and find out what they say are the rules they have for refilling tanks. If you buy a large 300/330 cu ft tank, they are cheaper to refill per cu ft. Ask about tank refill costs and see how much difference there is.
Those large tanks are generally for industrial customers and many/all suppliers WILL NOT refill them unless you have documented proof of ownership from the company who sold you the bottles....and many will not sell large bottles to individuals. Signed reciepts from individuals or auctions are not valid ....at least in my state...and they say its a federal law. On the other hand a company in Az told me that was a lie. So check out what they say in your area.
Anyway, the tank will have a cast in name at the top of the bottle so you can tell who owns it. Problem there is that these gas companies sell out to larger companies with different names. All is not lost though, because there are tanks that actually have no name cast on them. Supposedly the problem is that it is illegal for a gas company to refill a tank from another company. If the tank has no name cast on it, then any company should refill it for you.
On the smaller tanks, they are usually sold to individuals so all of what I said above normally doesn't apply and any company can fill them....but check with your local supplier to verify .
You can usually buy tanks very cheaply at auctions and somewhat more expensive on Craigslist. Doesn't matter how ratty they look....you can paint them later. What you want to look for is the type of gas they held. Tanks almost never go bad and some of the ones in service are almost a century old. Tanks can be purged and switched to hold different gases
in some cases . Normally most people use a 75/25 mix for mig welding. 75% Argon 25% CO2
Almost any used and abused tank you find is going to need to be recertified.
When you go to buy a used tank, that is a good thing to point out to the seller in order to get a better price.
Tanks cannot be refilled if they are out of certification.
You also might check with your local gas distributor and see what they charge to do a recertify. If they don't do that, ask who they send their tanks to for recert. If they won't help, then find another company that will. My local company sends them out and takes about 2 weeks to get them back. Bout $40 I think. Anyway, take your tank to them and when they recertify it they will also refill it and you are good to go....for 10 years.
At the top of the tank there will be some larger numbers stamped which signify the date of certification. Next to the numbers will be a + and a star. That means its certified for 10 years. Watch the video below for a better explanation.
When I get a tank, I sand it a little and paint it close to the color that it had on it. Then I make a stencil and paint my name on it in a bright color near the top. I also write what kind of gas I want in it....like ARGON or 75/25 . Then it stands out easily when you pick it back up.
