93 V6 dual rear wheel RV. Inside of gas tank is heavily rusted, outside is pristine, no dents, no rust, no leaks.

I am looking at my options on this, the replacement tanks have a bad reputation, have looked at the aftermarket tanks, obviously poor quality and will not be using one.

So now am looking at a Por 15 tank kit. I do see a couple things that need addressing. The sump in the tank has small channels to keep the fuel from rapidly leaving the sump I would guess. I can see where the tank sealer would plug these but think I can clean them with compressed air before the Por solidifies. Good idea bad idea??

There is a 1/4" line leaving the tank which I think goes to the charcoal canister?? The line crosses the tank inside and terminates on top of the tank in an odd looking thing. What is it, what is its function, will the por plug it? I do not have a large hand and I cannot reach it. Any suggestions on what to do with it?? Here is the best pic I could get of the thingy, picture is not from old tank.

 

A guess would be a pressure vent, which I'd imagine does run to the charcoal cannister so it doesn't vent to the atmosphere.
if it got plugged during your gas tank POR coating the one drawback I can think of filling the tank at a service station. The pressure build up may keep disengaging the pump. But that's pure speculation.

 

I’ve used phosphoric acid to de-rust gas tanks before with great success. I buy the high concentrate acid 85% and dilute to 20%. Pour a gallon or so into tank and slosh around periodically to keep inside surfaces wet. Time and acid do all of the work.

once acid is removed rinse thoroughly then apply a good coating of light oil like WD 40 to prevent surface rust.

 

When I removed old tank, not the one shown in picture above. It was soooooo bad inside I was not sure if it was worth saving. I took it to a shop recommended by NAPA to have it looked at. They said the tank is worth saving and will clean and line the tank for $225. So I left it with them, they figure about 10 days.

Thanks for the comments, greatly appreciated.

 

im assuming thats a vent line to keep from vapor locking the motor