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Shelf life of Proseal

Michael Burbidge

Well Known Member
Does anyone know what the shelf life of unmixed Proseal is. i.e. How far out is the expiration date marked on the can?

I'm trying to decide whether to order with my Wing Kit or not.

Thanks,
Michael-
 
Each can has a shelf life, I've had a few cans and if I remember, one had 6 months left and I think one may have had 8 or 9 months. It depends on when Van's or your supplier gets it and how long it sits on the shelf. Some people put it in the freezer so it stays good longer. I finished my tanks late this summer and I put the remaining can in the freezer just in case I needed it for something.

Don't order proseal for fuel tanks until you need it. Yeah, it costs for shipping, but you really want fresh stuff for that.
 
i have kept a can in the freezer for at least 3 yrs and use it still. sets up the same as the day i got it. i wouldn't use it to seal tanks but as long as it mixes and sets up i have other uses for it.
 
12 months from manufacture

The quart kit I got from Van's had a 12 mth expiry from manufacture. Made in August '19, I got it in early November, and have just started on the second tank with it.

I suggest you order it when you're ready to seal the tanks. There's a lot of prep work on wings and tanks that can take a long time to do. Buy the quart kit, it's much easier to just mix up what you need, sometimes you only want a few grams of sealant for a small job.
 
This is not a recommendation, just a datapoint.

We've had an expired quart kit of proseal in the frig at the hangar for over ten years. It has come in handy many times for various adhesive tasks. Eight years ago I built a tank for the Legal Eagle with it, last year I modified the tank on the D.VII, and this year I sealed the transmission on the '48 Plymouth with the same quart. :) It has always cured as it should.

If I was building RV tanks I would definitely start with a new quart. But I wouldn't be concerned if it expired prior to finishing the second tank. If you get all the prep work done on both tanks you can seal a pair in a month. Here is the log for my RV-6 tanks which were completed in one month:

http://home.hiwaay.net/~sbuc/journal/tanks.html
 
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Like Bob said, I'd use best practices for the tanks (meaning fresh can) and then keep the leftovers in the freezer for non-critical applications down the road such as the cabin air NACA inlets. I still have some in the freezer from 2012 ish.
 
Proseal

I resealed one of my tanks after removing slosh. I used Chemseal which is the same as Proseal for less than half the cost at A/C Spruce. I used the 3.5 oz tubes. It took 5 tubes for one wing. The 5th tube was for the 5 plates for the holes I cut in the rear baffles so you would only need 4 per wing. Buy the metal stirrer for $15 that attaches to the drill to mix the tube. You?ll be glad you did than by mixing it by hand twisting the plunger. I would scott brite all areas where you are applying the proseal even though it?s not necessary. If the person would have Scott brite the inside of tank before applying the slosh the slosh wouldn?t have separated from the tank. Slosh is some tuff material.

For those of you who have slosh in your tanks that you want to remove it you can use professional strength Goofoff liquid and it removes it real easy like 20 seconds. It softens proseal but it?s pretty tough. When I do my other wing I?m going to use the gel to see if I can leave it on there longer as opposed to flooding the tank with a couple gallons of the liquid which I did not do. I just soaked a rag and left it on an area for a few minutes
 
MIL-S-8802F

Proseal is supposed to comply with specification MIL-S-8802F.

The spec requires a shelf life of at least 9 months when stored at 25 C and 50% RH (section 3.4.21).

In addition, the shelf life can be updated provided the sealant continues to meet various conditions. These basically say that if it looks ok, mixes ok, cures ok, and develops at least the minimum peel strength it's ok to use. Each shelf life update provides a 3 month extension. Up to 3 successive extensions are allowed (section 4.1.3.2).

Based on my observations of extensive use of PR-1440 on military aircraft, provided you store it in cool, dry conditions it will easily meet the life extension conditions.

In our case, I'd say order it around the time you need it, from a reputable supplier who has stored it properly, and you'll have no problem meeting the spec at least twelve months after you receive it.

It may last much longer, and normally does, particularly for applications like aerosmoothing, but after 18 months it will no longer officially meet the specification.
 
Flamemaster

The Flamemaster stuff Vans sells is fine but I agree. I you can wait till the tanks are started, your stuff will be freshest. That said, mine is years old and I use it for all sorts of non-fuel tank stuff. Recently patched my Thermorest mattresses!:D
 
Proseal

Just an FYI. Back when I was working fore the big boys we would keep all silent, epoxy in a freezer. Thus extending the shelf life by 2. Then we would test, (mix a couple test batches) if the test mix was still good, it got another 6 months. We would often see proseal with 3or more extensions. Just mix a small batch spread it on an peeve of aluminum, scuffed of corse, and put a piece of wood on top. If it holds the wood to were the wood splits. When you pry it from the aluminum. It?s still good. The stuf seams to last forever in the freezer.
 
This is not a recommendation, just a datapoint.

We've had an expired quart kit of proseal in the frig at the hangar for over ten years. It has come in handy many times for various adhesive tasks. Eight years ago I built a tank for the Legal Eagle with it, last year I modified the tank on the D.VII, and this year I sealed the transmission on the '48 Plymouth with the same quart. :) It has always cured as it should.

If I was building RV tanks I would definitely start with a new quart. But I wouldn't be concerned if it expired prior to finishing the second tank. If you get all the prep work done on both tanks you can seal a pair in a month. Here is the log for my RV-6 tanks which were completed in one month:

http://home.hiwaay.net/~sbuc/journal/tanks.html

+1. Just can?t throw it away. I just keep it cold.
 
Thanks

Thanks for all the responses. Last time around I spent way too much on shipping. I'm determined to batch up orders this time to save on shipping.

But I'll probably wait on the proseal.

Michael-
 
I do the same as some of the other replies here: Used fresh Proseal for sealing the tanks, and I keep the rest in the fridge for other odds and ends. Purchased 7/1/2017, and it still (as of last application) cures and sticks like super glue.
 
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