Coating a Fiberglass Tank with POR-15 Clear

[454MRW]

I usually pick up my POR-15 CLEAR at automotive swap meets, but there are sources on-line that sell it as well. It seems that the amount of Alchohol in the gas which is ever increasing is the reason for the problems with the tanks. I have had a tank that never had any problems start to exhibit bubbling of the original gel-coat, but I don't drain my tanks usually.
Here are the directions that I have provided some other people inquiring on the application for coating the inside of a fiberglass tank.

I first wash out the tanks 2-3 times with Lacquer thinner to remove as much traces of oil as possible, rinsing them for about 2-3 minutes each time and after the last rinse, I wash it again with MEK, (Methel Ethel Keytone), or Acetone should also work, to remove any remaining traces of moisture. MEK is very toxic, so avoid breathing the fumes or allowing skin to come in contact with it. Acetone can be use in place of MEK, but doesn't have quite the drying capability as MEK. Once the final rinse is complete, the tank will be stickly on the inside due to the thinner starting to break down the fiberglass resin. Care should be taken not to over do it and collapse the tank.
The POR-15 product I use is POR-15 CLEAR and requires no metal prep. I do use the POR-15 brand thinner and thin the mixture about 15-20% to aid in ease of swishing it around in the tank. The POR-15 websites states that is should only be thinned 5%, but thinning it a little more only slows down the time it takes to initially set up. POR-15 should not be used with any other brand thinner according to them.
I remove the petcocks and insert temporary plugs or rolled up white duct tape in the holes which can be easily removed and reinstalled before the POR-15 CLEAR sets up. To do one tank I used 1/2 of one pint plus the thinner and once poured into the tank, I tape over the filler neck and rotate the tank several times and then drain it back into a separate container through one of the petcocks, which requires rotating the tank several more times to get the majority of it out. Once sufficiently drained, I remove the other petcock plug and the tape from the filler neck and position the tank so that any remaining POR-15 CLEAR will pool in the lower rear area of the tank, which is prone to wearing on the frame cushions and often leaking.
Periodically check for drips coming out of the petcocks and wipe away any drips to avoid plugging of the petcock holes and requiring inserting a drill bit and cleaning them out before the POR-15 fully sets up. After about an hour check the tape removed from the filler neck and once it becomes tacky, repeat the whole process again 2-3 more times, and when finished let the tank set open for a couple of days and it will be ready for use.
BTW, The fiberglass that I coated in POR-15 CLEAR and soaked in Lacquer thinner never did become soft or sticky.
A pint of POR-15 CLEAR thinned 15-20% should be enough to coat 3-4 tanks if done at the same time. Once removed from the original can, do not pour it back in with the unused POR-15 CLEAR or it will cause it the unused POR-15 CLEAR to prematurely set up. Seal the lid of the unused POR-15 CLEAR with some wax paper between the lid and the can immediately after removal of the amount to wish to use, and store it in a cool place for later use, but if any gets in the groove of the can lid, you will probably have to puncture the can to get the lid off.
Preparation for coating the exterior of a tank only requires sanding into the Gel Coat and cleaning the prepared surface with Lacquer thinner. The POR-15 clear is best applied with a brush, as thinning it enough to use a spray gun will usually cause tiny bubbles in the coating, and will require finishing with a brush anyway. Once the POR-15 Clear becomes tacky, repeat the coating process at least 2 more times. POR-15 instructions state that while still tacky your favorite primer/prep coating should be applied to bond with the POR-15 Clear to allow you to later sand the primer and apply paint. POR-15 is a very hard coating, but it can be sanded and painted later if you like hard work hand sanding for a smooth finish.
 
**Update 10-21-2011** It has been recommended by POR-15 representatives that Lacquer thinner should not be used, as it leaves traces of oil behind which can caused adhesion problems. Instead they recommend the use of POR-15 Marine Clean, which is a water based cleaner and let the tank sit a day to dry or use forced air to speed drying prior to coating the tank. Mike
Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[DKWRACER]

Mike, excellent write-up, and thanks for the POR-15, it has proved to be a very good product. Am currently working on a new 76 MC5 to be dubbed the "Black Jackel" some-zing like you have never seen b-fore.

Tom Brosius
Mile High Pentons

[pketchum]

Mike, thanks for the write up for applying POR-15.  Doesn't the external application of it using a paint brush leave brush marks that would require sanding?


Phil

[454MRW]

Phil,
The POR-15 flows out and smooths very well, maybe too well when thinned a little, even to the point that you have to be very careful, (and patient), to avoid runs. That is why I prefer to let it cure then use the elbow grease to sand it smooth before priming it for paint. A heavy coat of primer might accomplish the same thing, but I prefer the old tried and true method of sanding with heavy grit, then lighter and eventually wet sanding before primer. mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[tvrc18]

Do you think the Por works better than Caswell tank sealer?
Terry

[454MRW]

I have never used Caswells, but I have never found ANY chemical that can penetrate or even soften POR-15 once it is cured. It may even be impervious to battery acid, as it works so well. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[VICTOR MONZ]

I read about you all sealing tanks due to the "current" gasoline products.  I always use C-12 race gas and have never had any leaks or tank trouble begin.  I am doing something wrong ?

Merry Christmas to you all....I woke up early this morning and much to my surprise my Berkshire and Six Day must have mated overnight and another machine showed up in the shop this morning !

There is a Santa Claus.

Victor  (Oh then I did really wake up and it was just a pile of parts, but I see another Six Day sprouting up)

Thanks to all of you for your prayers this year....my racing is over due to health issues, but let the projects begin !

[tvrc18]

Is the POR 15 clear different than the standard  tank sealer? I see a cycle tank repair kit on the web site but it has metal prep included.
Terry

[454MRW]

I don't use tank sealer. POR-15 clear can be used as a improved substitute for the resin used in fiberglass repair. The tank sealer is just a sealer, not a permanent bonding resin type material for fiberglass. I have never tested any of the sealer to see if it would maintain its resistance to chemicals. Generally gas tank sealer is primarily designed for metal tanks.
In my opinion the POR-15 Clear would be much better at adhesion, and since it resists all chemicals, I don't see why you would want to use anything else.
The colored POR-15 is not a good candidate for tank coatings, because UV exposure tends to make it become chalky and weakens its coverage and requires a top coat of regular paint to protect it. The POR-15 clear only slightly yellows from UV exposure from my experience. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[tvrc18]

I see the clear called Pelucid single component clear coat. Is this what you are using?
Terry

[brian kirby]

Its the standard POR-15

http://www.por15.com/POR-15/productinfo/1GB/

It comes in black, gray, silver and clear.

Brian

'72 Berkshire

[chicagojerry]

i see that they have 4 oz 6 packs available.what do you think, mike? is that the way to go?  by the way, i have done some tanks with caswell and i'm not pleased with how it holds up to alcohol laced gas. i won't use it anymore.   chi jer

[brian kirby]

I was thinking the same thing Jerry. My Dad gets it in gallons because he uses a LOT, but I think those 4oz cans thinned a bit like Mike does would be perfect for 1 tank at a time.

Brian

'72 Berkshire

[454MRW]

I didn't see the 4 OZ 6 packs before, but sure, why not if you are only doing one tank. Just make sure you use their thinner to make sure it is compatible with the product. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[tvrc18]

Is the thinner you use what they call the solvent for clean up and thinning of the rust prevenative paint?
Terry