[BusNit]

My propane tank is a 67 gallon big boy. It is 31 years old with surface rust and my concern is safety. I can't find a replacement online that size or even a smaller one that has the fill ports on the end cap. I'd hate to lose the propane since my coach has two propane furnaces which work great and do not depend on much power to run. Not sure what to do. Last year I turned the gas valve on and it hissed a leak past the stem seal and "popped" itself sealed again.

[folivier]

Simon if it's only surface rust that can be easily repaired if removed.
The valve seat should be able to be replaced if the tank is empty also. Look up the DOT exemptions on propane tanks.

[hypoxia]

Not uncommon for the valve seat to leak, I use a brass drift or a screwdriver and tap it with a hammer to get them to seat. As Forest says, surface rust is not a concern. Rust pitting would be a concern. If the valve stem leaks when in between fully open & fully closed I would repair that the next time the tank is empty.

[BusNit]

Tank is empty now. Surface rust is at the bottom where exposed to the road. Do the interiors of these things rust? If the fuel/water separators were not in front of the tank, I would remove the propane tank and have it powder coated. I do not want to mess with the old diesel water separators since the fuel lines are hard in that area. That is a project for another time

[HoosierDaddy]

POR 15 the outside. They don’t rust on the inside.

[folivier]

I wouldn't think rust inside would be a problem. Propane is a petroleum product and over the years anything heavier (oils) would have dropped out. There should be no moisture present in propane. You'd probably notice it if it would, you'd have freezing inside your regulator (not on the outside).

[Latitude 28]

POR15 the outside.....have you ever heard of the stuff.......just messing with you LOL. You probably should a wholesale distributor of the POR products by now.

[Trainer]

Another excellent rust killing product is Ospho, a dilute solution of phosphoric acid. Scuff the surface and liberally apply Ospho. It will chemically change iron oxide to iron phosphate, an inert salt. Once dry, the surface is primed. Spray, brush or roll your choice of paint and you are done. Mo vapors to worry about and no rust in the future.

[BusNit]

Is the valve something I can replace myself or are there specific types? Tank overall looks ok. I would still rather pull it to do a good job but again, the fuel water separators are right in front of it and the fuel lines are hard so I do not want to disturb them just yet. I've got enough on my plate with this thing. I guess my fear is some propane filling stations may refuse to fill it due to age of tank/coach? I have a local place that won't do any work on coaches older than 20 years. Their sign shows they can refuse to fill propane based on their discrepancy. This is what made me think about all this.

[Latitude 28]

Another excellent rust killing product is Ospho, a dilute solution of phosphoric acid.  Scuff the surface and liberally apply Ospho.  It will chemically change iron oxide to iron phosphate, an inert salt. Once dry, the surface is primed.  Spray, brush or roll your choice of paint and you are done.  Mo vapors to worry about and no rust in the future.

My dad used Ospho on the boats when I was a kid.... brought it home to use around the house and I still use it today when needed!