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Kit 1 (2 oz. sealant)Kit 2(3.5 oz. sealant)
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Kit 1: 2.5 oz cartridge (Fill: 2 oz. sealant)

Kit 2: 6 oz cartridge (Fill: 3.5 oz. sealant)

CS3204 is a fuel resistant sealant for use on integral fuel tanks and pressurized cabins as well as other areas subject to contact with aircraft fuels, lubricants, oils, water and/or weathering.

At room temperature, this two-part polysulfide cures to a flexible, resilient rubber.

Meets requirements of specifications AMS-S-8802 formerly MIL-S-8802, CMNP021, Lockheed, Gulfstream, Hughes Aircraft, Fairchild SPS 6-1 & 6-2

Technical Data: Class B*
Cure Profile B-¼ B-½  B-1 B-2 B-4
Application Life (hrs) ¼  ½  2 4
Tack Free Time (hrs)  6 8 15 24 36
Cure Time (hrs) 16 30 40 72 90
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Had a leak in an integral aluminum fuel tank that hadnt been sealed properly since built. Worked superbly.

November 24, 2018

Used sealant to repair obsolete 30 year old plastic fuel tank

Neil C
September 14, 2018

Frank S
May 25, 2018

I really like this product. I use it at work on aircraft, and purchased it here to use at home on my airstream trailer renovation.

Joe S
April 6, 2018

Worked as advertised. Used the mixing tool in my drill and mixing was easy and fast. So far fuel tank is sealed up tight and nothing leaking. Hope it lasts for many years to come.

Terry B
March 16, 2018

Addition... Mixing: I clamped a slow speed drill (pointing up)in my vise and chucked a hole saw (backwards) that had holes that (nearly) matched the plunger handle of the tube. A couple of #8 screws, and I now had a power mixer. Turn on the drill (CW) and move the tube full stroke up and down 50 times (overkill) or so. Dispensing: Like a previous reviewer, I just used a cheap $5 gun.. mine didnt even require making the plunger diameter smaller.. it fit perfectly...

James S
March 16, 2017

Used this (B-2)for sealing the fuel sending unit into the side of a wing tank. All is well. I would probably use the faster version next time (B-1/2). Cures very flexible, not as hard as Proseal, but it is a polysulfide product (like Proseal) so we will see how long it lasts.

James S
March 16, 2017

Although I waste more than I probably should, I never have any issues with these kits not curing properly. I bought a cheap caulking gun and ground the ram down a bit on my bench grinder so that it fits the plunger on these tubes. Presto! $5 proseal gun! (use a zip tie to make sure the tube stays anchored in the cheap big-box store caulking gun)

Dana R
January 24, 2017

This sealant works awesome. It cures to a hard rubber and really seals. After trying a different sealant and it not working, I was desperate to find something to seal up my fuel tank. This stuff fit the bill and is completely leak free.

Chet R
June 3, 2015

...make sure the metal is bare and clean, i had a wing tank neck/nipple that i had to have a welder extended higher to work with my newly built wing tanks, after welding he gave a shot of spray paint on where he buffed the metal. After i threaded the nipple/neck into the top of the wing tank, I smeared the sealant on the inside of the nipple at the junction of the threads in addition to putting sealant on the fine threads. The sealant i had on the smooth part of the inside of the nipple started to lift because of the spray paint the welder put on after welding.

Ken K
June 18, 2014


Q: What is the maximum operating temperature of Pro-Seal after it has cured?

It has a service temperature range from -65*F (-54*C) to 250*F (121*C), with intermittent excursions up to 275*F (135*C).

Q: Is this Pro-Seal product compatible with methanol?

The tech data sheet only refers to aviation and jet fuel. It has been used in race vehicles that use many alcohol type additives without any known problems, but the supplier will not recommend it since it has not been lab tested.

Q: What is the shelf life of the unmixed product?

The shelf life is 9 months from date of packaging.

Q: Will Pro-Seal cure to a rigid state or will it remain flexible for repairs on a fuel bladder?

It will be flexible when cured, but we recommend verifying with the bladder manufacturer this material can be used.

Q: How do you mix this Pro-Seal tank sealant if you didn't purchase the mixing tool?

Per our product support manager: The user would have to pump and twist the ram manually by hand. The mixing tool saves a lot of time and effort.

Q: Does ethanol attack or dissolve Pro Seal over time?

Proseal has been used in ethanol applications, but the manufacturer has no documentation to provide to show how well, or how long, it will work.

Q: Will this Pro-Seal type tank sealant adhere to a plastic tank?

This will adhere to a plastic tank but will eventually breakdown because of the gasoline. This is mainly used for aluminum and titanium steel. This would not be recommended per supplier for a plastic tank.

Q: How do you dispense from these cartridges? Can they be used with a Semco gun and can you use a caulking gun like you would find commonly?

After the cartridge has been mixed, you can use a manual dispensing gun, p/n's 12-38520 or 12-38530, or an air-powered gun like 12-02923, 12-02922, 12-02921, or 12-02920. A Semco, or other common caulking gun is not designed to be used with these sealant cartridges.

Q: I only need to seal a small hole so I only need a small amount. Is this Pro-Seal Type Tank Sealant CS3204 similar to epoxy to mix and use?

It is self contained, and designed for a one time use. The two parts, A&B, are already properly measured, so the two parts are mixed in the cartridge until one uniform color and then you install the nozzle, and push rod, then just apply to the area.

Q: How much surface area will the 3.5 oz kit of Chemseal B2 sealant cover? I want to make sure I have enough product to seal my entire surface.

This will all depend on how thick you are applying this. However there is a formula that will help, if you apply this to an area that is 1" cubed so 1" length x 1" height x 1" depth, it would use exactly 1.8047 fluid oz.

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