Fuel Tank Relining/Coating Stories

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Don L

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Joined
Mar 7, 2023
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612
I would like to read owner stories of relining and/or coating leaking fuel tanks as to what was involved and what did it cost.
 
I have no story, but I have heard of airplanes using "slushing compound" for small leaks in fuel tanks.
 
Por15 is a respected name in coatings. They make a fuel tank sealant. Over 2700 reviews and 160+ questions answered. May give you some decent info. Missing link is access to the inside of a tank given baffls and such.

https://a.co/d/akYAd1l

Peter
 
I used a 3 step Eastwood system that was intended to seal tanks from the inside. But I used it on the outside to seal the rust.
Came out super smooth but it’s toxic to work with. Respirator required.
 
I have resealed black iron tank. I looked on line and found a system that required an etch then a seal along with a two part putty to fill larger holes. They wanted to pull the tank and "Slosh" the whole tank. Unable to remove the tank, I had a large inspection hole on top I was able to access and coat while in the boat. Only coated about 1/3 up as that was where it was leaking. Tank lasted 15 years until I sold boat and have not heard anything about a leak since.

Second issue an aluminum tank, leak along a weld at back bottom of tank. Cut an access hole in top, used a product called "Seal All" available at Ace Hardware et al. You take strips of an old T shirt, impregnated with this Seal All ( comes in big tube like model airplane glue and smells the same) and lay strips over leak. That has worked for 5 years now. I swear by this stuff. Both tanks would have had to been cut out of the boat as boat built around the tanks. Saved my bacon for sure.
 
mvweebles said:
Por15 is a respected name in coatings. They make a fuel tank sealant. Over 2700 reviews and 160+ questions answered. May give you some decent info. Missing link is access to the inside of a tank given baffls and such.

https://a.co/d/akYAd1l

Peter
Click to expand...

My old boat neighbor used POR 15 in a older Taiwanese trawler with iron tanks. A professional cut access holes, cleaned the inside of the tanks with the POR provided solution, which smelled just like 409. Then there was the solution which re-converts rust to metal, then the sealer on the inside. All following the POR instructions. The pinhole leak returned in two years.
 
I have no experience with fixing a tank by coating the inside.

I have pulled and repaired tanks from the outside. I have also pulled tanks that turned out to be not worth repairing.
 
Slightly off topic -

If one were purchasing a 30 to 40 year old yacht with metal tanks, would coating the tanks before there was a leak be prudent decision?

I am assuming (maybe wrongfully so) that coating the inside inscluding cutting and sealing an inspection hole is less money than tank replacement. Also assuming a metal tank will eventually leak or need replacement.
 
Action said:
Slightly off topic -

If one were purchasing a 30 to 40 year old yacht with metal tanks, would coating the tanks before there was a leak be prudent decision?

I am assuming (maybe wrongfully so) that coating the inside inscluding cutting and sealing an inspection hole is less money than tank replacement. Also assuming a metal tank will eventually leak or need replacement.
Click to expand...

To it would depend on the tank and the cost. But if you could inspect the tank well enough to clean it well enough to coat and didn't see any reason to do the coating I wouldn't coat it unless it was cheap to so so.
 
Seems a lot more stories here on TR about replacing tanks than relining or coating them ( I did search before posting the thread!). But if you go to a company site of those doing it there are lots of positive stories of course. Which is why I started the thread.
 
Don L said:
To it would depend on the tank and the cost. But if you could inspect the tank well enough to clean it well enough to coat and didn't see any reason to do the coating I wouldn't coat it unless it was cheap to so so.
Click to expand...

Not sure the words boat and cheap go together.
 
Had an older 1985 Taiwanese Trawler with Black Iron tanks. Port tank began leaking. Hired a guy in so cal. He cut a larger inspection port in the side of the tank. Cleaned out the tank really good. Actually had the guy crawl inside the tank. Then coated it with 3 coats of an airplane tank sealant on the inside (he called it that). Tank held fuel fine for the 3 years I had the boat after that.
 
Don L said:
They do, but you have to understand boat cheap meaning
Click to expand...

My understanding of "Boat Cheap" is called dingy.
And yes I did spell that correctly.
 
Don L said:
Seems a lot more stories here on TR about replacing tanks than relining or coating them ( I did search before posting the thread!). But if you go to a company site of those doing it there are lots of positive stories of course. Which is why I started the thread.
Click to expand...
Curious - are these companies doing 200g baffled tanks, or 6g motorcycle tanks? Do they have the tank in their shop where it can be rotated, or are they working on it in-situ?

Another active thread asked about possible cost of replacing saddle tanks. Pictures he posted showed a lot of stuff mounted to breadboard protecting tanks - lots of electrical and plumbing stuff. Just getting to the tanks would take heroic measures.

Peter
 
Years ago I had a leak at a welded seam on a steel tank in my lobster boat. The tank was 40years old. I patched it, from the outside, with Por15 liquid then paste. Now, 10 years later, still dry as a bone.
 
Don L said:
I would like to read owner stories of relining and/or coating leaking fuel tanks as to what was involved and what did it cost.
Click to expand...

There was a gentleman on the T&T List (some of you may remember that original boating list) who had a great deal of experience maintaining his 1985 CHB Taiwanese trawler and kept detailed records on his web site. Unfortunately, he is no longer with us and his web site no longer exists (this was back in the early 2000's). However, I still have all of posts from that list, going back to 1998 until it closed in 2021 and I've checked his posts to see what he recommended; actually he had several solutions.

No matter what method is used, the basic requirement if doing it from the inside of the tank is to get it as clean as possible. For this, he cut a 14X14 inspection port in the side of the tank (after emptying all the fuel, obviously), then spraying it was a soap and then a degreaser solution multiple times, sucking out the residue as best as possible. Make sure to clean the baffles on both sides, as well.

On one of his tanks he had a welder close all the pinhole leaks. On another he used a sealant which was sprayed on the interior (I haven't been able to come up with the product, but there are certainly a number discoverable on the internet which would be impervious to diesel fuel). Ventilation was a key, and when welding from the inside he kept the exterior cool with a piece of wetted plywood. One of the tanks had to be raised from it's bed in order to perform the work (probably the welded tank).

I actually talked with him about the process at one point in 2004/5 when I was trying to figure out what to do with the fuel tanks on my then 1986 trawler (Hampton 35 - a 25 production made in Taiwan). He favored the spray coating as being easier, and for him it didn't seem like a big deal. I felt otherwise, and opted to remove the tanks and have exact duplicates fabricated from stainless steel.

At the time, 2005, the two 100 gallon tanks cost $1000 for both. The total job (removing two engines, removing the tanks, replacing everything) cost less than $4,000.

Ten years later I did the same type of thing with our 1987 DeFever 41 which had a single FL135; the old tanks had to be cut out of the boat as the boat was obviously built around the tanks. When fabricated, divided each tank in half lengthwise and vertically when they were rebuilt by taking a 1" rectangular section out of the design for the original tanks (only lost 10 gallons per side doing that) and fabricated out of heavy-duty stainless steel which would meet CG specs for passenger vessels. Did a lot of other work in the process including upgrading a lot of fuel lines, CG double-crimped line fittings, new vents, etc. Turned out the original tanks on the DeFever were advertised as holding 400 gallons total, but the new tanks (almost exact replacements minus the 1" section) held a total of 528 gallons (total of both tanks). The cost of the four new tanks, heavy SS, cost a total of $10,000. Labor for just the tank work probably ran about $20K.

A lot of the work is documented on our web site (which is still up) at MVSanderling.net/Blog if you're interested in taking a look there.
 
Sealed my day running tank with 2 part polysulfide coating on the inside.

Hello,
My 85 Marine Trader 43' Labele black iron day tank had a small leak that I repaired with a 2 part poly sulfide coating used for lining aircraft wing tanks.

Steps:
1) I drained and pressure washed inside of tank with TSP solution, rinsed to remove TSP detergent.
2) Filled the tank with water and washing soda and descaled it using electrolysis with a battery charger and iron sacrificial anode. You can search the internet for reference how to remove rust with electrolysis.
3) Treated the inside of tank with a black oxide rust converter. I used a water based product purchased from Walmart. Rinsed it and air dried the tank with fans for a few days.
4) I rolled on the polysulfide coating coating purchased from a air plane supplier on line. I used a few gallons (not cheap). When it sets up the tank has a rubber coating that has held up for 3 years so far.
Note: my leak was more of a slow weeping where the outside of the tank came into contact with water in the bilge. I cleaned and coated the outside area of the leak on the tank with some of the poly coating.
I also added 9" inspection plate on the fuel tank top for better access to the repair area. My tank had 2 inspection plates, but i added a third using rivet nuts, rubber gasket and 10" round steel covers.
I also had to create a floor pull up door to access the new inspection port.
 
Steel Tanks

I was talking to my father who lives in Oregon about the Steel Diesel Tanks on boats. He's not on the coast but not too far from it. He said he sees hundreds of old Steel Diesel Tanks ( used for heating) sitting outside in the elements with no leaks. These tanks are commonly used for heating oil/ Diesel many like his over or close to 100 years old.

I am wondering if it's the Marine Environment or maybe the motion or maybe it's not as common as we think it is for Old Trawler Diesel Tanks to leak?
 
Most tanks in older boats are not "steel" but rather black iron, which rusts from the inside due to accumulation of moisture in the diesel fuel or from the outside due to water leaks sitting on top of the tanks or around the base.
 
I have slushed small tanks, and it does work, however, the key is thoroughly cleaning, de-oiling the inside of the tank, every square inch, weld, baffle, corner, fillet etc. I believe that's not possible for a large, conventional diesel tank. Even tanks I have hot water pressure washed, my preferred method of cleaning, aren't clean enough for a coating, especially true of tanks with more baffles. If you have a breach of the coating in just one place, at a fill neck, or supply fitting thread, fuel will migrate beneath the coating and it will begin release.
 
I agree with Steve D. That's why I decided to replace the tanks on both trawlers. It's just not worth the work to take a chance on getting the inside absolutely clean enough to let any coating adhere.
 
BobMc said:
Most tanks in older boats are not "steel" but rather black iron, which rusts from the inside due to accumulation of moisture in the diesel fuel or from the outside due to water leaks sitting on top of the tanks or around the base.
Click to expand...

I believe, in the vast majority of cases, they are actually not iron, but "black iron" entered the boat building lexicon long ago and has remained, most are in fact steel, which of course does rust. Some, few in my experience, are black steal, which has a higher carbon content, which actually makes them more corrosion resistant, but harder to weld and more brittle. Conventional steel, while clearly not a first choice, especially if it's thick, can last a very long time in tank applications. I'm involved in building an 85 foot steel vessel now and naturally its tanks are steel (and interiors are uncoated).

Black Steel
Black steel is made by adding carbon to iron during the smelting process. This creates iron-carbon alloys that are harder than pure iron but more brittle than other types of steel. Black steel has a matte finish that does not rust or corrode as easily as regular carbon steel due to its higher carbon content levels. It is also highly resistant to wear and abrasion due to its hardness, making it a popular choice for structural components such as bridges and heavy machinery parts where durability is essential. However, its hardness also makes it challenging to work with – cutting or welding requires special equipment and expertise.

Carbon Steel
Carbon steel contains up to 2% carbon, iron, and other elements such as manganese, chromium, vanadium, tungsten, nickel, molybdenum, copper, and titanium. Carbon content affects the strength and hardness of the material but also increases brittleness, so care must be taken when machining or forming the material into specific shapes. Carbon steels are heat-treated after fabrication to achieve desired properties such as increased strength or improved corrosion resistance. These steels are easy to cut and weld, making them great for general fabrication use, such as frames and brackets for machinery or piping systems for industrial applications.
 
Fuel tank repair

I've successfully used 2 products from JB Weld to repair a visible small leak on a steel tank.
#8217 is a putty stick that you knead together & press or clamp on the affected area for about 15 min. #2110 is a piece of fibreglass tape and mixible packets of of epoxy that heat up and harden REAL Fast!!!
They work. A hint...its easier to properly do the job if youn empty tghe tank. Bob
 
Fuel Tank Repair

I have been doing a very extensive refit on a 1987 Kadey Krogen 36 up here int PNW. The boat had been on the hard for quite awhile due to the owners wife having Alzheimer’s. The boat has all stainless water and fuel tanks. The fuel tank is 280 gallons with huge clean outs in the aft vertical surface. I had the tank pumped out, cleaned out and the clean outs left open. I crawled into the tank and did another super clean out. The tank wasn’t leaking but, I had the idea of finding a stainless steel welder to re-weld the seams from the inside. Made one phone call and the mobile welding guy told me he had a young man who worked at the Anacortes ship building place and was an artist with stainless steel. They showed up at the boat yard next day, rigged up a fume vacuum system. The young man climbed into the tank and welded all the bottom and vertical seams. He is an artist. The welds are beautiful. The stainless 150 gallon water tanks sat empty for several years and are perfectly fine. The owner installed a new Yanmar diesel engine and transmission in 2008. Poor fella only got to put 146 hours on that motor before his wife became Ill and he let the boat sit. In my long life I have finished two large sailboats from a bare hull and have owned two trawlers before this one. A Kadey Krogen 42 and a Camano 31. I bought this boat as it is a great boat and was well worth saving. I will probably sell her when I finish the refit due to my age. Someone will end up with a real fine boat?
 
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