By the time you clean, and de-rust the tank you can spend a little more and buy a new one without worrying about the rust coming back. All you have to do is miss one little spot and 2 years from now while you are coming home at 2am the tank will start leaking gas all over the place leaving you stranded. Of course this has never happened to me. lol Tanks inc. specializes in building tanks for most of the old cars. I would at least price a new one with them before attempting to fix the old one.
Get a Tank from Tanks Inc.They are Poly and are great!! I won't take the time to tell you of the grief I experienced with my 48 Merc.and a steel tank.About 220 Bucks and your troubles are over.
I've had two years of problems because I was using an 80 year old tank. I've flushed the fuel lines numerous times, had to clean the carb out almost daily for a year and even installed a furnace filter on top of the normal feul filter.
I would go a buy a new one (something I don't like saying) but the cost and risk associated with it, thats what I would do.
You didn't say if you had Ford, Chevy, Dodge, or Studebaker. Regardless, the good folks at Rock Valley Antique Auto Parts in Stillman Valley IL can make you a new STAINLESS STEEL tank using your old one for a pattern if you don't have a popular make that they already do.
I've used several of their tanks and they are primo. You can specify what sending unit hole pattern, TPI style electric fuel pump mounting and on and on. Short turnaround on custom builts and very quick delivery on stocking tanks.
They are great. Tell Dave I said HI!
i have had good luck with a franchise called gas tank renew, they clean out your old tank then dip it in a special plastic type material and you get no leaks forever and a good looking affordable job. we even use it on oil pans that are impossible to get replacements for, good stuff.
The only thing that I found cleans the 30 year old sludge is straight acetone - I fill to the level of the sludge line then let it set for a day or two. I dump the acetone thru a filter back into a container - most tanks that I have done this way take about 3 gal. of stuff. The filter is nothing more than a metal screen - then whatever doesn't get filtered usually just settles to the bottom.
After this I use Zep rust/calcium remover (from Home Depot) w/ a 50-50 mix of water and let it work for an hour or two to clear the rust. *I think this is phos. acid*
I use muriatic acid to clean them out. Eats the rust away no problem. You just have to block off the fuel line holes and fuel sensor hole with rubber. Let it sit on each side for about 30 min. or untill you can see the rust is gone.
After that I flush it with water a times and them use the por tank sealer to finish up. Unless a large hole pops up then i braze a patch on before using the sealer. Never had a problem.