I've used REDKOTE in three different tanks, two tractors and the one on my 47 Lincoln. No problems yet, the Linc has been done over 5 years now. Follow the directions, clean good.
I believe we have discussed this in the past but I can add my 2 cents again. I have sealed quite a few tanks for customers and myself with great results, no failures. Preparation is the most important part of the process, the tank must be surgically clean inside. The sealer I use has chemicals to clean then etch the tank, the sealer itself is the final step. https://www.kbs-coatings.com/tank-sealers.html If you do the prep and let the sealer cure you will experience good results. One tip: the tank needs to be rotated to make sure the prep and sealer get to every part of the tank, I rigged up my engine stand to accept a tank then all I had to do was “spin” the tank on the stand, much easier than shaking the tank by hand.
I did the tank I built for my Model A with a POR 15 kit. It has a cleaner, an etcher and finally a sealer. It's a pain in the rear to do, but I'm happy with the results.
I cleaned a tank with lots of rust inside with a piece of heavy chain, some corse sand and soapy water first then did the POR15 sealer kit. Still solid after 4 yrs. A hair dryer blowing in the tank dries the water very fast.
Historically, if you do a search I bet you will find 75+% will say don't do it, sealers WILL cause problems down the road.
Just to share my personal experience, I sealed the tank in my Karmann Ghia back in 2005 with kreem. I had some issues with my fuel gauge about a year ago and I pulled the sender. When I looked inside, I could see some pretty good size bubbles in the kreem on the top inside of the tank. It's yet to be a pressing problem, but it has me worried.
Back in 1970, I sealed the gas tank in my '29 Ford with the latest and greatest gas tank sealer. When the new ethanol gas came along we learned that it would destroy the sealant. Everyone had issues, some had the sealer come off in sheets, some people had the pieces clog the jet's in their carburetor's. Fast forward to about 2015 and Bill Hersh Products ( not sure of the spelling) came out with sealer that is impervious to the ethanol gas. So far so good until the government comes out with another new gasoline mandate. I would suggest that if you don't need it, don't put sealer in your tank.
If you read the por15 website it says the coating is only good for about two years.I never researched the other coatings.One thing I noticed is if you watch some of the you tube videos of guys getting cars that have sat in a field for years running and driving they usually just stick an extra filter before the pump and change it when ever it clogs up.Not saying this the correct way.I have thought about putting a two cycle mix in the tank just to slow down the process.
The place that coats the tanks where I work drills holes in them between the baffles and sandblasts the inside of the tanks before coating. Then they solder up the holes and coat the inside.