WE use a Landa Kerosene fired pressure washer... leave the wand in the tank for 20 min or so with it boiling out.
Then if any rust, some metal prep, then coat with 2 part tank sealer from POR15. We have done countless Harley tanks and 20-30 car tanks, never had a problem with any of them even with ethanol fuels.
Had bike customers who used tank liner and once it started to peel it left them stranded on the road. I do a lot of custom artwork on bikes. Strange how some of my cars have been sitting for decades have zero tank issues.
I'm going to go out on a limb and assume it was not you who prepped the tanks
VERY FEW laypeople are meticulous enough to correctly prep a fuel tank for coating.
My dad's original 1940 Ford Woodie wagon tank (which had surface rust inside prior to being boiled and blasted has been coated near 30 years now & Have done I cannot tell you how many bike tanks over the past 10 years NEVER once had an issue with coating failure.
As you know it's ALL in the PREP.
If I boiled them out and removed the rust without coating them, the bike would be back at the guys shop inside of 2 years with the same tank corrosion issues.
