[rotorwrench]

One of the common sealers is a red color so I would want to look in there to see if there has ever been any sealer put in there other than the factory coating. I use a bore scope to look inside. I can see top and bottom surfaces and it's long enough to peer over the edge of the baffles to see how the outsides look. A person can carefully scrape a little bit off the bottom to see if there is rust in there. If it's rusty then it has to all be removed to reseal.

I used to use Drano crystals when there were thick varnish deposits in a tank. The original Drano is no longer available so now I use Black Swan crystals. Caustic soda will remove about anything and it only takes a day or so. The caveat of using it depends on the condition of the original tank lining. Model A tanks were internally coated at the factory with tern plating. Caustic soda will remove everything in there but the steel and the corrosion. The baffles make the corrosion removal a very difficult thing unless the tank is cut open. This is a very time consuming task so unless a person is equipped to do it themselves then it will be expensive. If corrosion is light then it can be chemically removed but if it's heavy and repairs are needed then that won't work.