Is it safe to use a rusted propane tank?
Accordingly, is it safe to use an old propane tank?
Assuming that the cylinder is in good shape, you should be fine to use an older cylinder, as the LPG-propane (bottled gas) never goes bad. Be sure to check for leaks around the valve before and after connection.
Also question is, how long can a propane tank sit unused?
Large stationary propane tanks must be recertified 10 years after their date of manufacture and every five years following that. A propane delivery company can refuse to fill your tank if it is not certified or if it is rusted or in poor condition.
The simplest and easiest way to clean your propane tank is using a garden hose and a brush. This method will clean light dirt and grime, but tree sap and mold and mildew will need more muscle. The next easiest way is using a pressure washer. When rinsing, use a pressure washer if available; otherwise use a garden hose.