Air Tank Question

Where can I have it re-certified and it expensive?

If it's out of date, it can't be recertified and its monetary value is zero. There is a company that was recertifying some brands but as far as I know, they were only doing it in bulk lots for large companies or organisations. The cost of the procedure made it not viable for the average Joe.
 
I got a couple tanks last year, a 30min and a 60min with valve and fresh hydro with 5 years left on age out, off Ebay. For under $150, add the fill system and your under $200. I also have a new 75CF slow fill valve and the cost per year is quite similar. So one can weight budget and if one is going to a compressor in the next 5 years and the xtra dollars can go toward the compressor. 
 
I got a couple tanks last year, a 30min and a 60min with valve and fresh hydro with 5 years left on age out, off Ebay. For under $150, add the fill system and your under $200. I also have a new 75CF slow fill valve and the cost per year is quite similar. So one can weight budget and if one is going to a compressor in the next 5 years and the xtra dollars can go toward the compressor.

Would you have a link for this? Thanks