Restoring a gas tank with a special derusting liquid?

Guys my daughter and us menfolk are helping her get a 1980 Volvo running. This is the girl who spiffed up Poncho Loco then flipped him for a nice profit. The Volvo gas tank is badly rusted inside but not perforated. I found a Volvo forum called TurboBricks and its denizens uniformly say the new Spectra etc tanks are crap thin in comparison. The OE tank we pulled does indeed feel very thick. The car sat for 4 years with the tank nearly empty.

I called all over for a gas tank restoral shop and only found one several hours drive for us one way. They want $250 and one week to do the job. So we'd have to make that drive twice  Nobody closer found. Lots of classic radiator shops have closed, folks just buy Chinese copy radiators now. Those radiator guys often also did fuel tanks.

One body shop owner I know suggested that old car hot rodders do gas tank reconditioning themselves with a liquid product. You pour it in, let it sit a few hours, then rotate the tank so another part is submerged, until the entire interior is treated.

Anybody know what that product is? I'm going to ask my local NAPA tomorrow. Old school guys, they know a lot.

They are probably talking about Damon's Red-Kote
It reeked of MEK, and that is what was used to rinse the tank after acid washing the tank but before applying the liquid.
MEK is all but impossible to find today so I don't know if they have reformulated.

My radiator shop guy used to do this but I doubt they still do (liability)
The process is involved. I'm sure it's not cheap.

I used to see this back in the days before oxygenated fuels but haven't recently.
Probably because, like you said, people just buy a new one that isn't rotted out.

I have used Kreem on motorcycle gas tanks. I’d think it would work on bigger tanks too.

One thing I learned is to do it exactly as the instructions say. I have had very good results with it. Cleaning it thoroughly is important.

https://www.kreem.com/fueltankliner.html

Ah yes, Methyl Ethyl Ketone, which we nicknamed Methyl Ethyl Deathyl. I always thought it was nasty.  Carbon tetrachloride was easy to get too. I'll probably die of them before I get to 100. We used to light balls of rags soaked in alcohol on fire and play catch. And blow up our sisters' dolls with M80s. We're lucky to be alive. Girls get murderously mad...

Anyway, our tank isn't rotted out, just rusted inside.  NAPA guys suggest Eastwood has a cleaning and epoxy kit that works.

Let us not forget DCM (AKA methylene chloride)   🥴
While it's not flammable it does burn like hell.
I suspect this was in the old Gumout that would crackle when you sprayed it out of the tube.

I don't know anything about Eastwood products, but I do know that POR-15 makes a tank sealer.
If it's anything like their other products it would definitely bond any rust inside that tank forever

there are products out there, but I would strongly urge to read online reviews because I know lots of people had issues with the fuel tank sealers that Eastwood and other restoration shops sell, not Eastwood brand it's the brand with the brass era car on the bottle.

The stuff worked well but with the ethanol blended fuels people started complaining about the sealer failing as it wasn't ethanol safe.  It might be now I wouldn't know; I have always opted for a new fuel tank over trying to salvage the old.

https://www.gastankrenu.net/
Look for a dealer near you.
I have a tank done by a place in PA over 10 years ago on put 5 gallons at a time as the cat is a project but still holds gas and I don't see any signs of it coming off.

I had it done as no one makes a tank for the car.
Dave ----

GastankRenu seems to be a big chain with big prices.

$680 quoted to me on the phone just now ... and I have to get it there, 2 hours away.

Crikey!!