I have an old tank of r134a . It is about half full. I don't work with 134a that much and when I do the it's a small system with less then 2lbs. I was cleaning the shop and came across the old tank it looks rusted on the outside. So my question is does freon go bad? Is the tank rusted all the way thru? Is the gas contaminated? I think maybe I should toss it and by a fresh bottle. However I don't like throwing away money if the gas is good.