I just obtained a 20# C02 tank from a friend. It was given to him about 9-10 years ago by a homebrewing buddy who quit and then gave him tons of stuff. My friend never used any of it. So I get this tank and its still full of c02. So my question is, does it ever go bad or stale? I don’t want to go using it only have it spoil my beer or something. And its not cheap to fill where I am at so I’d like to use it if I could. To my knowledge the tank has been kept in good conditions this whole time.
In my experience i have used an old tank from 1995 with CO2 inside to slow carbonate my cream ale awhile back and everything turned out fine for me. This was about 3 months ago, also i do not think that CO2 gas goes bad if you leave it.
Why don’t you just call your supplier and ask them that will put your mind to rest.
Because my supplier is a welding shop and don’t know anything about applications to beer.
I hope this helps bolster your confidence in my advice
http://www.homebrewtalk.com/f35/does-co2-go-bad-327677/