POR-15 coating fiberglass tanks

[454MRW]

**10-21-2011**I received a call from Tony Friedel about a couple of Penton tanks that he coated with POR-15 Clear per the instructions that I previously posted on this site. One of the tank coatings were bubbling and the other was coming loose in sheets. I called POR-15 and spoke to Mark, inquiring whether there had been any change to the formula, since Chicago Jerry had a similar problem with the coating that I had applied myself, and my thoughts were that there may have been traces of oil or contaminants remaining in the fiberglass of the tank causing the POR-15 Clear to not adhere properly. It had also been noted that the coating was now more of an amber color than in applications more than 3 months ago.

Mark claimed that there had been no changes to the formula, that the POR-15 Clear had always been a slight amber color, and that the use of Lacquer thinner was not recommended as a pre-cleaner prior to coating, as Lacquer thinner supposedly left a residue that they had previous problems with. I have seen a post on Marks Swap Meet page regarding Caswells tank sealer that recommended not using Lacquer thinner as a pre-cleaner and according to them, it left traces of oil behind and they recommended using Acetone before coating with Caswells products.
As in my instructions, I had mentioned using a follow up rinse with MEK to further clean and dry and remnants of moisture prior to the coating, but Mark strongy suggested using their product, Marine Clean, a water based cleaner to remove all contaminants from the tank, instead of Lacquer thinner, and allow the tank to sit for a day, or force air dry the tank to evaporate and water prior to coating.
I will be ammending my instructions on this site accordingly, although that would not explain the effectiveness of the coatings done prior to the past 3 months, or as long as 2 years ago. Mark also noted that their thinner, which was used occasionly, only has a shelf life of 4-6 months at the most and should not be used if older than 6 months. They also recommend their POR-15 fiberglass tank sealant, although it is a slightly softer product and would not stiffen the tank as much as the POR-15 Clear.

Matt at POR-15 stated that their paint stripper should be able to remove failed coating from a tank without damage to fiberglass, but I feel care should be taken to avoid weakening the tank and I can provide instructions on application of the stripper if needed.
If anyone is having problems with the POR-15 Clear, please let me know and I will continue to provide updates as I try POR-15's recommendations. Mike [email protected]  


Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Tom Murphy]

Mike, I coated a tank within the last 2 months and it has bubbled up pretty severely, and is amber in color. I purchased and used the marine clean for two complete wash cycles and let air dry for a week before application. I am glad to hear there might be a way to strip as I was thinking the tank was trashed. I have two more tanks to do and only by chance did I not do therm all at the same time. I'm glad I didn't. Keep us posted and thanks. Tom

Tom Murphy
'73 250 Hare Scrambler
'73 125 six day project
'74 125 six day
'81 RM125
'82 RM250

[454MRW]

Tom,
If I might ask, what do you refer to as two complete wash cycles? How much Marine Clean did it take? When I was previously rinsing them in Lacquer thinner, It took 4 or more 5-6 minute agitated rinsings to make the last rinse come out perfectly clear on some tank, occasionly using a gallon or more of Lacquer thinner on each tank before I was satisfied with the appearance of the last wash, prior to a couple of final rinses with the MEK. Although POR-15 claims that nothing has changed in the formula, I don't remember the coating having near the amber tint that it currently does. Thanks, Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[Tom Murphy]

Mike, you're thinking the same thing I am. The tank started with a fair amount of goo so I rinsed 5-6 times with straight gas until it seemed pretty clean. I then mixed the marine clean with hot water per instructions, agitated good, filled the tank and let sit overnight. Next morning I mixed up more marine clean, agitated and rinsed. It seemed pretty clean but I can't help but think I should have done this several more times. I think I will go the lacquer thinner/MEK route with another tank that is ready for coating.   Any reco's on using the stripper correctly would also be much appreciated. Tom

Tom Murphy
'73 250 Hare Scrambler
'73 125 six day project
'74 125 six day
'81 RM125
'82 RM250

[Tom Murphy]

One more thing...
Be careful using Marine Clean. I was cleaning parts and a chain in a bucket with this and tore a hole in one of my gloves so I just kept on washing. I washed my hands good afterward but the next day my hands felt like I had acid burns on them!  Tom

Tom Murphy
'73 250 Hare Scrambler
'73 125 six day project
'74 125 six day
'81 RM125
'82 RM250

[454MRW]

Tom,
My gut instint is that the failed POR-15 is due to oil or ethanol remnants that have over time imperviated the gel coat inside of the tank and if it is true about Lacquer thinner leaving an oily residue as suggested by the Caswell site, it may be better to use Acetone to do all of the rinsing, and not using the more hazardous MEK at all, since Acetone its self acts as a drying agent.

I am unsure at this point, but I doubt that a water based cleaner such as the Marine Clean could penetrate the gel coat to thoroughly purge the oil or contaminants from the gel coat in the tank.

Getting the POR-15 to initially bond to the fiberglass gel coat is the key and in the first coatings I performed on these tanks utilized the Lacquer thinner to not only clean the tank, but also to soften the gel coat to a slight tackiness and the Mek to remove and trace water left behind by the Lacquer thinner. This should also be a characteristic of Acetone, without the need for MEK, and the coating could be applied while the tank remained tacky if the Acetone if drained completely and the coating applied soon after the rinsing.
Care should be taken that the tank does not get too soft if the Acetone is left too long in the tank and should be closely monitored while rinsing. Email me for stipping recomendations, as I have an in depth proceedure. Thanks, Mike [email protected]

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S
1975 Can Am 175 TNT & 77 250 Black Widow
1979 Husqvarna OR390
1976-78 RM & 77-79 PE Suzuki's
1974 CR250M 07 CR125R 79 CR250R

[paul a. busick]

Hi fellow POGERS,
  I have been following this tank sealing problem for sometime and wish to add my 2 cents worth to the topic.
  As a small boat builder and mold designer for the HI Point trailers I have some experence with fiberglass and resins.  I have tried (unsucessfuly) to find out what type of resin was used to make the Penton tanks. That being said, I think that the resin used was a general purpose polyester resin.  A polyester resin is fine for somethings but not the best for gas tanks.  A few years back in the marine industry there was a problem with blistering of the hull gel coat. Gel coat being made with a high grade resin with a high density. Much was studied about the problem.  It was found that that the chemical differences between the water in the bilge and the outside water was causing the migration (osmosis)of the water in the bilge to outside water thus causing the blisters to the exterior gel coat. It was decovered that the cheaper boats had a application of gel coat applied to the interior of the hull to cover the poor workman ship of the layups.  The sandwiching of the general purpose resin with the gel coats, halted the osmosis.  The lesser quality hulls didn't blister, unlike the better made hulls. More tests were done with different resins and gel coats and the problem was corrected by using a vinylester or epoxy resin.  
  Which leades me to the question, has anyone tried sealing a tank with epoxy resin?  Epoxy being a much better grade of resin and better suited to the application of building gas tanks.  The West System by the Gougeon Bros. of Bay City, MI, has many types of epoxy resin and are very helpful in steering the customer to the correct application. //www.epoxyworks.com  866-937-8797.
  I would also submit that Polytek Mold making materials might also be a cure.  They have many types of pourable materials that might stand up to the new fuels. //www.polytek.com  800-550-8620
  While the above methods may be somewhat on the expensive side.  I think that the out come would be highly favorable.  After all, how many times can you try the same repair with the same results?
See you down Old dusty.
Your humble and most obedient servent,
Amherst Paul

[kenbike]

I coated my tank in May of this year with POR 15 and used acetone to clean the tank.  As I recall it did soften the inside of the tank and I was concerned I had used it too much.  I did the POR 15 application and it was amber in color.  It still appears to be holding as of today.