Fuel tank sealer

[hid3]

Hello community,

I need some advice from people who has knowledge or experience dealing with fuel tank sealers.

I've got an oldtimer car (I think that's called a 'classic car' in the US) and I'm having problems with fuel tank.
Long story short, I am on 3rd fuel tank right now. All of them are suffering from internal rust and eventually they start leaking gasoline.
To make matters worse, the fuel tank is located inside the cabin so once it starts leaking, you feel strong gasoline smell and diziness is felt too.

The original tank I removed from the car was so bad that there was nothing to weld/solder. Entire bottom was rusted and I found millions of small holes after pressure washing it and flushing all the rust out.

The 3rd tank, which is installed now was given to a local tank & radiator specialist to identify problematic areas and fix it. So he did some soldering (or welding? IDK) on it. One year later, the tank developed a leak, and I think in the same spot where it was repaired.

I managed to find a used fuel tank in fair condition. It contains some rust inside but nowhere as bad as my previous tanks were. Since replacing the fuel tank in this car is a PITA, I'd like to do it the last time, that's why I want to use some tank sealer before the installation.

Since I'm located in the middle of Europe, finding some professional-use chemicals is next to impossible. Best what I can find is some epoxy for 'emergency fuel tank repairs' but that's not what I am looking for.

So I decided to look for US-made products. What I found so far are those:
1) POR-15 Fuel Tank Sealer
2) Red Kote fuel tank sealer.

I also came accross some other less known products but they had mixed reviews so I decided to skip those products.

Does anyone have any experience treating old fuel tanks? Which product should I use?
The tank itself is 45 liters / 12 Gallons in capacity, yet it has a bit complex shape - 3 baffles inside and filler neck goes a bit deeper into the tank making some kind of barrier if you put the tank upside down (not all fluid contents spill out in that case; not sure if my explanation is clear). Also, I need a sealer which would be resistant to high ethanol content in gasoline.

POR-15: Pros - good reviews, available for purchase in UK so that I can order it easily. Cons - very expensive, considering I'd need somewhere between pint and a quart of actual sealer

Red Kote: Pros - not too expensive, comes in a quart can which should be sufficient for the job. Cons - unavailable in UK or Europe, shipping it from US might be problematic/impossible.

Any input highly aprreciated.

Thank you

 

[Donald]

I used a fuel tank sealer kit. It was an involved process to use the prep chemicals and then the sealer. But mine for for a 2 or 3 gallon tank for a welder/generator.

A lot of prep. One of the parts of the process had me rotate the tank round and round so the chemical re-coats the tank every hour for several hours.

It was definitely more work than just pouring in the sealer, rotating it round and round a few times then pouring out the sealer and letting it dry.

 

[Lubener]

I never had any long term success with sealing a rusted tank. I wouldn't waste my time on a used tank unless it came from the southern states. New, aftermarket tanks are available and are not very expensive if you want to do it once. I replaced the front tank on my 87 F150 back in 1997 with a Spectra. To this day, it is still shiny and rust free. I remember smearing grease on the tank where the straps went. That is where most of the leaks occur.

 

[hid3]

I used a fuel tank sealer kit. It was an involved process to use the prep chemicals and then the sealer. But mine for for a 2 or 3 gallon tank for a welder/generator.

A lot of prep. One of the parts of the process had me rotate the tank round and round so the chemical re-coats the tank every hour for several hours.

It was definitely more work than just pouring in the sealer, rotating it round and round a few times then pouring out the sealer and letting it dry.

I think I've read your posts here when I was searching for fuel tank sealer subject in this forum before creating this thread.

I never had any long term success with sealing a rusted tank. I wouldn't waste my time on a used tank unless it came from the southern states. New, aftermarket tanks are available and are not very expensive if you want to do it once. I replaced the front tank on my 87 F150 back in 1997 with a Spectra. To this day, it is still shiny and rust free. I remember smearing grease on the tank where the straps went. That is where most of the leaks occur.

You mean you had failures even using POR15 or Red-Kote products?
New fuel tank for this car is not available.
Used fuel tanks are all rusty, some more, some less.
Aftermarket fuel tank for this car is definitely not an option because of its specific shape. And manufacturing a custom one of stainles steel is way above my budget.

 

[Asterix]

When your fuel contains ethanol, a urethane sealer is the only option. Epoxy dissolves in alcohol. Most of the tank repair goops are epoxy, so will not last no matter what the label says.

I recall that POR15 is a urethane. Surface preparation is absolutely key to success. As clean as possible and free of any rust is the way to start. Perhaps in your case external sealing would be easier. Sounds like your tank is a crazy shape. It would be easier to clean and prep the outside of the tank then coat it with a urethane sealer, likely from POR-15. Read the safety and technical datasheets to make sure it's urethane-based. External coating would not be as good as an internal one, but you do what you can.

Perhaps consider having your shop weld any big problem spots first is in order before and prep and coat. Welding to be liquid-tight is difficult. TIG is the best option with some inert gas flowing on the other side of the weld to minimize oxidation there, too. Filling the tank with argon before welding is preferable not only to reduce the change of explosion.

Also, when your fuel contains ethanol, regular doses of Sta-Bil (or equivalent) is in order because the ethanol sucks up water out of the air.

 

[hid3]

I've bought a replacement tank which is in fair shape. It has sat dry for 20+ years in a garage, yes it has some rust inside but nowehere as any other of the tanks I had.
That's why I want to preserve this tank as best as possible.

Completely removing all the rust and crud is easier said than done. The tank has a long filler neck and two 1.5" holes for fuel pickup and fuel level sender. The best what can be done in this configuration is to drop a chain inside, wiggle it for some time and then use a vacuum cleaner with a hose attached to vacuum out all the residue.

However, my original question is about the internal tank sealant - should I choose Red-Kote or POR15.
All fuels nowadays contain ethanol, everywhere in the world. Some regions have E10, others have E20+. So I believe modern tank sealant should account for that.

 

[Dave Sherman]

I just went through repairing the gas tank in the '47 Lincoln in my signature. The tank on that was very rusty, but hadn't leaked yet. There were also no replacements available. The POR15 kit was expensive, but it was worth it. I first filled it with 20 gallons of white vinegar for a couple days to get rid of most of the surface rust, then rinsed with baking soda and water several times to neutralize the acid. I threw in a box of wood screws and shook it up with water, that also loosened up lots of rust.

The POR15 kit comes with a cleaner and a surface prep solution, those both take a while to get it thoroughly clean, and the prep involves rotating the tank several times to get the phosphate coating applied. I think the hardest part was getting all the loosened rust out, I must have filled, shook, and dumped the tank 30 or more times before I stopped getting flakes out of it.

Drying the tank after rinsing out the prep solution was the next hard part, I used a heat gun blowing into the tank, but it took over an hour before it was actually dry. It's imperative that the tank be completely dry before you try to use the sealer. Applying the sealer isn't hard, but it is messy and it takes a while to drain the excess off. It says it takes 96 hours (4 days) to dry, but it still smelled strongly of paint fumes, it was more like a week before the smell wasn't too noticeable.

I used POR15 (not the whole kit, just the sealer) on the Honda motorcycle's tank since it had also rusted. The vinegar treatment took out most of the rust, but I had to remove the fuel petcock first as the POR15 would have clogged up the screen and the valve. Did that about a year ago, and there are no signs the coating is flaking off. I'll say again, the preparation to coat it is the hard part, it took lots and lots of rinsing to get the rusty flakes out.

 

[hid3]

Dave, I've also read you thread here on your Lincoln tank restoration. TBH, I was suprised the tank had pretty thick metal not to start leaking after that much rust you extracted from it plus the woodscrews abrasion.

I don't really care about the curing time of the sealant. Since this is not my daily driver, I am fine leaving the tank to cure for weeks if needed.
Mainly I'm worried about the following things:
- Not being able to extract all the water/moisture from the tank
- Flashrust on the tank surface right away after washing/rinsing it
- loose and crunchy phosphates which will form after using 'Metal prep' solution which might prevent proper adherance of the POR15 to the surface
- fear of Red-Kote or POR15 being too viscous and not reaching all the areas inside the tank; especially the vertical baffles. This might cause failue and peeling of the coating

I've watched a dozen of fuel tank restoration videos on YouTube for both, Red-Kote as well as POR15. Under each video there is at least one comment from a person saying "don't use this product, it failed for me"

 

[Nessism1]

I have restored a number of motorcycle gas tanks that have had rust inside. The choice of which sealer to use depends on the condition of the tank.

If the tank is structurally sound, with just surface rust, it may not need to be sealed. You must derust well, though (obviously). For tanks that have good metal, but significant rust, Por-15 is what I use. It's basically a paint. Moisture cure. They claim it can seal over rust, but don't do it. You should fully derust to the greatest extent possible before sealing. For tanks with more significant rust, where pinholes form, I use a two part epoxy, as sold by Caswell's Plating. It's super thick, and will reinforce the metal in the tank. Hopefully, there are similar products you can find in your area.

There are various ways to derust, most involving acid of some sort. Vinegar works, but it's very slow. It may take a week or two to fully derust the tank. What I use is phosphoric acid. It's the pro's choice in paint shops and so forth. You can dilute it with water to fill the space. Higher concentration will work faster.

Before derusting you need to remove all gasoline varnish first. The acid sauce won't cut through the varnish easily. Maybe take the tank to a radiator shop and have them boil it out? That may remove some of the light rust also. A bore scope would be useful to check for rust during the cleaning process. The quality of results depends on your diligence.

 

[Dave Sherman]

I was concerned about the flash rust, and even after rinsing the metal prep solution, there was a little bit of surface rust forming. The instructions said that was normal. I gather the sealer might work better if there is some light surface rust for it to bond to.

I was concerned about the baffle in the Lincoln's tank, it took some more sloshing when I looked through the sender opening and saw it had missed the center of the baffle. That took some careful tilting to try to get it to run over the whole baffle. I stuck my borescope through the opening in the baffle, and at least it appears to have coated the far side that I can't see.

Yes, I've seen the reviews and Youtube videos of POR15, and there's always a few that say it didn't work even though they followed all the directions. I can only figure either they had a spot that didn't get coated, or maybe it wasn't fully dry. Still too early to say if I was successful on the Lincoln, but from what I can see through the filler neck I don't see any strange spots. The sediment bowl on the pump is staying clear. The motorcycle's tank is holding up and I don't see any flakes in its sediment bowl.

 

[Devo242]

I have used the POR-15 kit and was very happy with it for my application. Below is a link to some photos I posted of my experience with the product to show my use case so you can review:

Post in thread 'Rusty gas tank help'

Aug 15, 2024

I have used the POR-15 tank restore kit recommend it. The car in question is 40+ years old and had been sitting for over a decade with ethanol gas and it seemed like considerable rust at the bottom of the tank.

I thought the tank a write off but thought I would take a shot at restoring it before buying a new one which is available OEM. I used a garden hose to remove the hardened rust at the bottom and it came out in chunks, turns out it was some sort of hard formation that I can only guess what it was but when removed it left behind was something I could work with.

The full POR-15 kit...

• Devo242

• 

This tank is from a Volvo 240 and appx 16 gallons in capacity with a baffle. I purchased the POR-15 kit plus an extra pint to ensure I had enough product. I could have skipped the extra pint as I dumped it and more out when everything was sufficiently coated, though perhaps having so much product sloshing in the tank made the coating process easier.

Important to note I spent a lot of time cleaning the outside of the tank from surface rust and painting that as well, though in the future I will do that after treating the inside of the tank rather than outside first, then inside like I did in this project.

 

[paulo57509]

I've used a product called Kreem. I believe it was one of the first products that came out for this purpose. I used it on a 1972 Yamaha CS5 fuel tank with great success. The tank had pin holes in the lower areas of the tank (typical).

It's a pretty straight forward process. I wasn't paying attention to the small cross over tubes on either side at the bottom skirts of the tank; the Kreem plugged one of them. I lost a bit of range; I used to stop and tilt the motorcycle over when it hit reserve. TBH, I don't know of an easy way to prevent his from happening. Just be aware of these little details.

Kreem | Fuel Tank Liner

kreem, kreem products, fuel tank liner

kreem.com

 

[Asterix]

For tanks with more significant rust, where pinholes form, I use a two part epoxy, as sold by Caswell's Plating. It's super thick, and will reinforce the metal in the tank. Hopefully, there are similar products you can find in your area.

Epoxy will not last at all in the presence of alcohol. The only material that will handle continuous immersion in gasoline with ethanol is urethane.

 

[nomas]

Is there a " new " after market tank available that wouldn't have existing rust issues ?

 

[Opelman]

I second Caswells. I did an antique tractor tank that was very holey after cleaning. Blue tape over the holes to hold in the sealer and success. One hole was almost large enough to qualify as a window. Better than 5 years ago with no issues.

 

[Nessism1]

Epoxy will not last at all in the presence of alcohol. The only material that will handle continuous immersion in gasoline with ethanol is urethane.

Feel free to call Caswell's and tell them they are full of $hit.

Phenol Novolac Epoxies are a new breed of chemical resistant materials, able to withstand permanent immersion of many harsh solvents, fuels and oils, including ethanol based fuels.

Caswell Epoxy Gas Tank Sealer - All Sizes & Colors

caswellplating.com

 

[Nessism1]

I second Caswells. I did an antique tractor tank that was very holey after cleaning. Blue tape over the holes to hold in the sealer and success. One hole was almost large enough to qualify as a window. Better than 5 years ago with no issues.

I did a somewhat rare motorcycle gas tank, using silver solder to close up some pin holes. During the derusting process, another leak formed, then another, and another. It was whack a mole trying to seal, only to have another pop up. I gave up, and started to tape over the leaks, like you did, and the tank sealed up nicely.

The sealer is killer thick, so I thinned it to the max allowable in the instructions, and it was still thick. I flowed it around the tank, coating all surfaces, then tried to dump the excess out, only it was so thick, it was taking too long, so I plugged the drain port and just rotated the tank again and again, adding a second coat so to speak. That tank could survive a nuclear blast after finishing. And a significant amount of weight was added in the process.

 

[hid3]

How did it hold up later?

 

[Number_35]

I've used the POR-15 fuel-tank sealer successfully on two old rusty and leaky fuel tanks. It worked well. Both vehicles died of old age before the fuel tanks presented any other problems.

Besides the internal sealer, in both cases I coated the outside with another POR-15 product, a black epoxy.

 

[Nessism1]

How did it hold up later?

I sold the tank so someone that still has it. To my knowledge, it's held up fine since he hasn't said anything, and I'm pretty sure he would let me know if started leaking.