Diesel fuel tank repair - internal coating

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Keith

Guru
Joined
Oct 5, 2007
Messages
2,715
Vessel Name
Anastasia III
Vessel Make
Krogen 42
I had developed a little fuel weep in my Starboard fuel tank. This is the original tank on a 1986 Krogen 42, hull #99. This was more of a nuisance than a problem about ½ cup of fuel would leak out per week, and I was using sorbent pads to catch it. The fuel was actually coming out of the forward bulkhead in the engine room and originally I had thought it was leaking from one of the fuel filters which are right there. Once I eliminated this, I knew the fuel was coming from the tank somewhere, running forward, and exiting from behind the bulkhead.

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I hired a local fuel tank repair guy to fix this problem. We first pumped all the fuel to the other tank, and then he cut three additional ports so that he could access each area of the tanks. There are four baffled sections, and I only had one inspection port forward. The main thing we found was rust on the upper portions of the inside of the tank, where fuel usually never gets, since I dont ever fill that high. This rust would fall off to the bottom of the tank, making a layer of crud down there. There was very little slime/crud other than that, so he scraped the bottom of the tank to clean out all this stuff.

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He then cleaned the inside of the tanks with a solvent. Im not sure what he used, but it smelled like MEK or maybe lacquer thinner. I also smelled alcohol, so maybe he used a mix. Naphtha would also work well. While doing all this, he hooked up a blower to the fill on the deck so it would suck the air out through the tank. We left this in place throughout the project. He essentially used a cardboard tube to make a riser out of the fill, and then put the intake hose from the blower over that.

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Once the tank had been solvent cleaned, he used an air grinder with some little 3 disks, maybe 60 grit to clean the metal down to bare and shiny. He then cleaned with solvent again.

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He coated the inside of the tank with some coating he painted on, ended up gray. Coated the entire tank from the bottom up to within about 4 of the top. He was very secretive about what he used, even removing the labels from the cans before bringing them to the boat. He did say it was a fuel tank lining used in the aviation industry.

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Here is a great .pdf file that explains aviation fuel tank sealers and lists three suppliers:
http://www.vansairforce.net/articles/tank_sealant.pdf

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Another good one, an aviation fuel tank sealer is at: http://www.sacskyranch.com/proseal.htm PPG Aerospace: http://tinyurl.com/ypwduq
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Searching the internet for aviation fuel tank coating, diesel tank repair or diesel tank lining will bring up other various repair materials. Some are designed to use inside a tank; some are for outside repair. Here are a few links:
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http://www.nationalsealants.com/Index.html http://www.hexaflex.co.uk/tuffcote.html http://prp-porstore.com/merchant.mvc?Screen=CTGY&Category_Code=TankSealers
http://www.pplmotorhomes.com/parts/caulks-sealants/40754.htm
http://www.piperepair.net/index.html
In any case, call the manufacturer to discuss the use with them.

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Another candidate comes from www.thinfilmtech.net. They have a product called GasPruf that is designed to line / remediate pipelines, petroleum tanks, etc. Its basically an epoxy. Here is a note from their spec sheet:GasPruf 130<sup>tm</sup>is a unique blend of liquid polymers and proprietary curing agents which is able to displace water or hydrocarbons such as gasoline or diesel fuel from wetted surfaces in order to make a permanent bond. The formulation is solvent-free to ensure safety and maximum technical performance. Kevlarä* fibers are incorporated for reinforcement and viscosity management to achieve high application rates -even under hydrocarbon liquids!
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I also imagine that you could use things like JB Weld or Splash Zone on the outside of the tank, if you can access it and find the leak.

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The seals for the new inspection ports were interesting. They were stainless steel, with a flat plate for the outside and two half-rings for the inside of the tank. He used them as a template to drill the holes outside the inspection port. He then threaded the bolts into the two half rings, sealing the threads with epoxy. He then made a gasket for the inside and outside of the tank, installed the two half rings inside with their gasket, then the outside plate with the gasket. The reason for the two half-rings was so that they could be passed through the hole. See: http://www.seabuilt.com/

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The repair seems to be working perfectly. The leak is repaired and I have a new set of inspection ports if I ever need to get in there again.
 

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Great article Keith, especiall since one of my tanks has a small leak if I put over 60 gallons in it. It is one of my 100 gallon tanks. I have been slowly gathering info on tank repair/replace proceedures.
 
He was very secretive about what he used, even removing the labels from the cans before bringing them to the boat. He did say it was a fuel tank lining used in the aviation industry.

Both Yamaha and of course Harley suffer from garbage fuel tanks , that dissolve from inside.

Patch kits are at their shops.

They do work for a while. Just a while .
 
Working great since 6/05. I figure if it's good enough to meet the safety standards of the aviation world, it's good enough for my boat!
 
The hard epoxies aren't a good call for any non-fixed fuel tanks, as there's always some flex when a boat/airplane/vehicle moves.

The tank sealers that Vans mentions are ideal.* The airplane that I sold last November had wing tanks that were simply a cavity in the wings between ribs that were sealed with PRC (see the Van's article, it's the PPG product now), and even had four inspection ports on the bottom of the tanks which were PRC sealed.* It sticks like hell, is flexible, and completely impervious to petroleum.* My airplane was 30 years old when I sold it, and the tanks were still tight.* And Avgas is a lot more reactive than diesel.

I wouldn't hesitate to use the PRC.

It doesn't seem like the stuff that he coated your tanks with, however, as PRC is more* like a cake frosting instead of a paint.

-- Edited by Chris Foster at 18:54, 2008-11-07
 
Keith: Good post and great pictures. It is a good alternative to replacing the tanks and I'm sure a lot cheaper.
 
Hopefully it will have an easier life in a boat where the temp swings will be easier to handle .

+20F to _180 F for a large return diesel, should be loads easier than sitting on the ramp at 140F and then going to -50C a couple of times a day.

Certainly its Better living thru Chemistry at its finest.
 
I ran across Keith's earlier post and thought it was well worth bringing up again. Great info!
 
Keith, any problems in the 2 years since you had the work done?
 
Nope, and it's been six years now.
 
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Since the holes were big enough to coat the inside, why not welded instead of just the coating?* Our middle tank, 400 gallons slit a seam, so I cut a hole big enough to climb into the tank, and had a welder weld the seam from the inside.* I was surprised how well the tank was.* If the*other tanks start leaking I will do the same thing, for this reason I fill the tanks ½ full to allow space*so fuel can be transferred.*
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I still think polishing, using additive, turning/using the fuel each year, and keeping the tanks at a relatively constant temp help to keep a tank clean.* Many boat*have 50+ year old tanks. *
 
Does know someone who does this sort of repair in the Fort Lauderdale area?
 
I did the exact same repair on my 1985 Trawler. Used the same aviation type sealant.
It's worked for 5 years so far.....zero leaks.
Sure was ALOT cheaper than replacing the tanks!
 
The stuff looks like Por15. Good stuff, have used it from the outside on steel tanks with good results.
 
Just a word of caution to anyone using this aviation sealant. It might be quite carcinogenic. Some types certainly were. One that springs to mind was the stuff used to clean or de-seal, the F111 tanks. Caused a lot of cancers here in Aus in the poor beggars who had to climb in and deal with the tank lining, and even electricians who has to do wiring after the job. Litigation over it took years to settle. So be extremely careful to wear proper respirators, not just the DIY woodworking type either. Just sayin'...
 
Can the thicker heavier coating be put on with a heavy nap roller? I am currently facing this repair
 
Can the thicker heavier coating be put on with a heavy nap roller? I am currently facing this repair

We coated the forward chambers with the Flamemaster 3204 Class A1/2 about three years ago just for pm. I didn't consider using a roller even though the A is suppose to be self leveling. It went on like molasses and sticks to everything it touches. The 3204 Class B is a paste.

Here's a picture of the Class A using a brush.

I talked to folks at Sky Geek. They were more helpful than the manufacturer.

Good luck with your project.

SkyGeek.com - Aviation Tools, Aircraft Oil, Parts, Sealants, Grease, Ground Support, Headsets & More!
 

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With bo-ig access and no structural baffels a bladder would be fast and easy.

A second advantage is the bladder can be removed , cleaned and re installed .
 
With bo-ig access and no structural baffels a bladder would be fast and easy.

A second advantage is the bladder can be removed , cleaned and re installed .

I did a little research into bladders and was left with the impression the fuel smell permeated the bladder
 
"I did a little research into bladders and was left with the impression the fuel smell permeated the bladder"

Perhaps a hassle for cockpit bladders used for a long delivery,

but the bladder in an old fuel tank should still be in an almost air tight steel box.
 
”Coated the entire tank from the bottom up to within about 4 of the top.”

I see this is an old thread, but I’m curios about the rationale for not coating the top. Wasn’t that the part that was shedding the rust?
 
Keith, if you are still on the forum, can you share the contact info of the person that repaired your tank. I know it's been a long time ago, but just maybe he's still around and can help me.
 
Keith passed away a few years ago. We miss him dearly. Keith started the “humor” thread in Harbor Chat.
 
I've built many metal tanks, steel, stainless, and aluminum, including tanks as part of the hull structure. When ever I build or repair a tank I coat it with a diesel or water approved coating. Properly coated, the tanks will last the life of the boat. If you can, coat the entire inside and if possible any welded in baffles, drains, fillers or vents. But especially bottom or sump drains. I always use diesel additives and they don't seem to hurt the coating nor does chlorine hurt the water tank coating.

Aircraft coatings are probably much more durable for flexing tanks (since aircraft tanks go thru many changes in pressure).
 
I've built many metal tanks, steel, stainless, and aluminum, including tanks as part of the hull structure. When ever I build or repair a tank I coat it with a diesel or water approved coating. Properly coated, the tanks will last the life of the boat. If you can, coat the entire inside and if possible any welded in baffles, drains, fillers or vents. But especially bottom or sump drains. I always use diesel additives and they don't seem to hurt the coating nor does chlorine hurt the water tank coating.

Aircraft coatings are probably much more durable for flexing tanks (since aircraft tanks go thru many changes in pressure).

Great point. I wish more folks applied a quality exterior epoxy coat. So many problems would be avoided.
 
Keith, if you are still on the forum, can you share the contact info of the person that repaired your tank. I know it's been a long time ago, but just maybe he's still around and can help me.

I'm not Keith (RIP) but I did the same repair myself.

Here's a link to a thread describing what I did to repair the tank. Many others here on TF have done the same, including Larry M and Wxx3.

https://www.trawlerforum.com/forums/s32/diesel-fuel-tank-sealant-36019.html

This is something that needs tank access ports and a modicum of skills. I hired a pro to cut the access ports and then I completed the job myself.

It spreads like sticky peanut butter. The toughest part is avoiding a sticky mess on everything it touches.
 
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