Here in Saskatchewan Canada where we park our bikes for about six months sometimes awful surprises surface such as the break down of the inner tank coating . This has happened to me .
The quest for best way to fix this was on. First drained, and removed tanks, used a camera snake to see all problems . Noticed rust and some of the coating still holding, it was a mess . I read about using tri sodium phosphate with a cathode anode current flowing through, would resolve the rust issues . So I hooked up a battery charger, to a couple pieces of steel from a coat hanger, and waited, and waited, cleaning and replacing them numerous times, it would work but the way I did it would probably take years.
I was aware of problems with the more common coatings available, and decided not to use them
I then went to a local radiator builder repair shop he wrapped up the tanks to try to protect the paint and then used acid to clean the tanks out . Then coated them with blue coat this was 5 years ago and still looking excellent inside . A year later my clear coat broke down, I had been warned about that possibility from the acid . No big deal about the paint I was happy to paint my tins anyway at that point .
Anyone else have this problem, and how did you fix it ?

 

Ahhh those rusty ole tanks!

Got Kreem, didn't do my tank. Why? Just some rust inside. Even after 20 some + years! Filter on mine works well with 10% ethanol. Just keep on it, if needed clean the petcock screen. For some reason the coating held well in '86.

 

Inside of my tanks seem good after 20 years. Maybe because the bike is ridden so regularly, I don't know.

 

I have had nothing but problems with tank liners and will not use them unless I have to. 01 sporty that had a cracked weld ( rigid fame) couldn't ven get local farmers to weld it because of the "unknown" coating. Solution ne tank and an excuse to repaint the bike. My 85 FL liner started to lift this spring so I added an inline filter and am careful when I put fuel in it slowly and will consider the options this fall. I have herd of muratic acid and drywall screws to remove the liner but it is a pain and then you have to get rid of the toxic wash.
I keep my tanks full during the winter with a high quality fuel stabilizer and avoide the grain crap the crooks are trying to sell use these days.

 

I want a snake camera! Got some oil leak behind the primary that leaves me a drip at the end of the ride. Wipe it off and no other oil forms until I ride.

But about my tank on my '86 FLTC... I had issues with the stock petcock, and the other 3 I had hoped would work. Finally broke down and paid the $100+ for a Pingel petcock and after some brilliant work cleaning up the float valve seat, some light sanding of the burs formed in the channel it sets in and a fresh valve I now have no overflow issues.

But to the point on the tank seal. I had a few strands of loose lining wrapped around the original petcock. I flush it all out and pondered redoing the inside coating. I decided I would take some time and consider what I could do. Well each time I had petcock failures, 2 drag specialties (I should have learned my lesson on the first elcheapo) and one used diaphragm style, I found only tiny amounts of debris. The last time, early this summer, I washed the tank down and flushed it I didn't have any particles show up in the clear glass container I was using, and nothing on the Pingel screen but a couple of tiny flakes.

So I know that I could take the time and money (and effort) and have the tank resealed but it's not a pressing priority matter.

And I agree with O/P that it'll be done by a careful repair facility, typically ones that repair tanks on cars, and I won't be playing chemists in my garage.

 

My tanks were bought raw when i painted the tins in 2005. I used Kreem and the acid etch kit that came with it. let it dry for atleast a week before puting gas in them...........they still look new inside today

 

Did you have any problems getting the rust out of the welding seam? I purchased a raw tank and it has been etched twice without getting the rust out of the seam, any suggestions?

 

I put a custom tank on a Sportster some years ago using the Kreeme products. I wasn't impressed. I don't have a good solution. I have heard all kinds of things over the years like using transmission fluid and BB's or screws to clean you tank out. How to seal it after the rust is cleaned is another question. I've heard mixed reviews about every product out there.

 

apple cider vinegar will eat up the rust inside the tank.....works great

 

Thank you Sno-Man!