Proseal Reversion Poll

Polysulfide sealant reversion ("My proseal turned to goo!") is an ongoing mystery. It's been suggested the issue is brand-related. Let's see if we can settle that one area of speculation with a simple poll. If you have suffered sealant reversion, or know someone who has, let's get the data posted.

Please be sure. No guesses please. Check the can, bag, label, invoice, packing slip, whatever you have, and be positive about the product ID. No one wants to see a supplier smeared unfairly.

Can’t participate as that can went bye bye 20 years ago. Whatever Vans sold as Proseal back then, if anybody knows. Never had an issue or heard of anyone else in that era have an issue.

Based on comments by Scott McDaniels the sealer that Vans supplied in 1995 and that turned to goo in my tanks was not a Flamemaster product, so I don't believe the failure is brand specific.

The facts for my tanks:
Built in 1995 and sealed with fresh Proseal (I understand) from Vans.
Tanks fitted with pre-made Vans fuel pickup tubes that came with sealant already applied around the screens.
Tanks originally pressure tested with balloon and no leaks.
Tanks then tested with 2-3 litres of avgas and no leaks.
Avgas evaporated and tanks stored dry until 2022.
In 2022 all internal sealant found to be reverted to goo. Including on the ends of the pickup tubes.
External sealant is all still sound.

My theory: when avgas ages and evaporates it produces a gas that causes the polysulfide sealant to turn to goo. Should not happen, but it does.

I've owned 4 Mooney's,3 out of the 4 had integral wet wing fuel tanks. 3 out of the 4 eventually developed tank leaks.

I never had one with runny pro-seal, which is quite common to see in RV tanks.
I think this is because Mooney uses a brushed on overcoat (PR-1005-L) applied over the bare Pro-Seal. It is definitely not tank slosh, it is brushed on (not applied anywhere except over the proseal).

I've never seen it come loose or flake off. It is my understanding it's purpose is to protect the underlying sealer from volatiles in the avgas. My experience (4400 hours flight time in Mooneys and performing annual inspections on many others) it seems to work for that purpose.

ive had it happen to flamemaster from vans, what ever AS sells in the small tubes and any other i have used over the years. i am convinced it is the additive packages in the fuel. i have never had it go to goo when in contact with liquid fuel. it alwas happens after a leak, the blue streaks form on the outside of the tank, and then the goo starts. i believe its the remains of the additives after the fuel evaporates that cause the breakdown.

bob burns
RV-4 N2RB