Final word on Fuel Tank prep and protection

[scphantm]

The tanks in the Stabbin Cabin are iffy at best. Close look at them tells me that they likely won't survive a boil. So, I started looking for tanks.

My first thought (from the boat world) is plastic. I have pulled countless fiberglass, steel, aluminum, and yes, even a few stainless tanks out of boats. Not one plastic. Even when they switched boats over to E85 and the fiberglass tanks started melting and the steel tanks started rusting, not even a little bit of problems with plastic tanks. So i started searching for plastic. Only https://titanfueltanks.com/ makes them. They have a beautifully manufactured tank, beefy 3/8 walls which is about the level of underground septic tanks. Beautiful piece. For $1000 and they don't make the front tank. We are not doing that.

So we are off to Spectra for some tanks. I'm getting them from Amazon for the free shipping but they are displayed here:

http://www.tanks-to-pans.com/site/823208/page/834501

These should be raw steel which begs the question, what about coatings.

Red Kote is crap along with POR-15. They are junk. Never seen a tank that didn't have problems with those two.

Have any of you come across an epoxy based system that holds up? doesn't crack when dented, holds up to poorly made BioDiesel, etc.

Also, what about the outside. Last time i did a car (15 years ago) the recommendation was to never coat the outside of the tank because it could sweat and rust. Is that still true today? I can grab a quart of marine grade epoxy and i assure you, nothing is getting thru it, but i was wondering what the rest of you have done.

 

[marmot]

http://www.por15.com/POR-15-Technical-Information_ep_62.html POR15 seems like it would be a good choice.

 

[BDCarrillo]

I think you'll be fine with an internally uncoated tank... look at how many of our trucks are running around 20 years later with a very low rate of tank issues.

The exterior could "sweat" in certain climates, but that's just condensation... a good paint should do fine on the outside.

 

[madpogue]

I wouldn't put anything inside the tank that might possibly end up in the fuel. Not to mention you'd have an effuva time reaching every last square centimeter of the inner surface, let alone knowing what parts you might have missed.

As for the outside, I'd love to see the preponderance of evidence that painting the outside makes the tank "sweat" (whatever that means). The only reason OEM tanks aren't painted is that mfrs are cheap, and they don't engineer anything on the vehicle to last more than 10 years. Up here, everyone I know paints the tank before installing it. Given that a completely bare tank lasts 10-15 years even here in the salt belt, almost anything marginally rust-preventive will do. Brush-on (not rattle-can) Rustoleum is oil-based. And like everything on the underside, it's good to spray it with a thin spray of Fluid Film every fall.

There are other plastic tanks out there. Jeff's Bronco Graveyard sells plastic rear tanks for the trucks; not sure if any would fit a van. Whoever makes their truck plastic tanks, they might make them for the vans too.

 

[scphantm]

, my preponderance of evidence? That education came from being a teenager and working for a 60 something year old mechanic with a short temper and a habit of throwing wrenches at you. Never paint it, if you want to do something brush on some engine oil, and under no circumstances undercoat it. first time since then that i had a need to question it is all.

 

[jay22day]

company's offer tank "dipping". Personally i think "dipping" is waste of money. My pops had his 87 jaguar tanks dipped/coated, i wasn't impressed but they don't leak and that car has sat a long time now.

I agree w/ madpogue

I wouldn't put ANYTHING inside a diesel tank, with diesel sloshing around it will keep the entire tank coated in diesel. Furthermore your fuel system shouldn't be acquiring moisture, or at least a extreme/concentrated enough amount that it could begin to rust the inside of the tank.

My tanks are 22 years old and have surface-rust on the outside, the inside of the tanks are beautiful, if the inside of the tanks begin to rust id expect the top seal to be the culprit.
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I have 6 years experience in refrigeration which surrounds around chemical evaporation. Chemical evaporation results in condensation (sweating) the principles are the same for a glass of ice water on a warm day or to the idea of a gas tank sweating on a hot day because the cool night left the fuel and tank very cold.

The tank and fuel have to be very very cold (from a cold night) and the atmospheric temperature (temperature in the shade, because tanks arnt exposed to the sun, being under the truck) has to be very high to achieve condensation (sweating) on the tank.

Theoretically the sweating will always occur on the outside because the warmer air holding moisture is outside of the tank (in addition, hopefully the fuel system doesn't have moisture in it, without moisture condensation cant occur).

In refrigeration foam, rubber, and "tar" (its probably a non hardening epoxy) are used as insulators to keep condensation localized to the evaporator (so it doesn't condensate or "sweat" on tubes leading to the evaporator that are outside of the back of the refrigerator.

As you can see, rubber is an insulator. By applying a rubberized undercoating, the tank will have a insulator all the way around it, coating it and reducing the heat transfer between the cold fuel within the tank and the hot atmospheric temperature outside of the tank. By reducing heat transfer with a rubber insulator, the cold of the fuel and metal tank touching it, are kept away from the heat and moisture of the outside atmosphere, the cold then cant condense the moisture in the warm/hot atmosphere because of the insulator around it.

Paint is pointless when trying to prevent condensation, as it doesn't have insulating properties.

Undercoating is a rubberized coating that will insulate (slow heat transfer), stopping or slowing condensation. It is a wonderful chip resistant protector/sealer. The thicker you spray the rubberized coating the better it will insulate.

The only undercoating i suggest is 3M Professional grade

The 3m professional grade is "rubberized" enough that it will act as an insulator and be very resistant to "stiffening/drying/cracking".

There are A LOT of REALLY CRAPPY undercoatings out there, i dont recommend anything other than 3m products and i stick to the pro grade.

If need be after a long time, products can be sprayed on old undercoatings to soften them and keep them soft and "fresh", if they ever begin to stiffen/dry.


Regardless of if you go with my suggestion, im sure what ever you do will be better than how it was stock. Good luck!

 

[scphantm]

Jay22Day, thats along the lines of what i was thinking too.

Now in the boat world, we HATE biodiesel. Most people put too much alcohol in it, which is hydroscopic, and when it sits in the tank, the alcohol absorbs water and rusts the tank out, or they don't wash all the lye out and that attacks the steel. Its a big issue on boats because boats can sit for weeks at a time without moving. I wouldn't imagine it would be an issue with bare steel insides on a vehicle tho. Is that a correct assumption?

I ask because a biodiesel refinery is further down on the todo list.

 

[jay22day]

First id like to point out i dont have extensive knowledge on bio-diesel. Although it is something id like to experiment with.
Some guys barely drive their diesel trucks, some are their everyday drivers. I heard some ugly things about biodiesel sitting, ive heard tails of algae like buildup, now as youve said, lye eating at the tank if not properly "washed".

I dont know that anyone has a "perfect formula" and until that is discovered i consider all that stuff "experimental" even though it obviously works.

what i can say is that when i start playing with biodiesel, i will most likely run a fuel cell in the bed for easy access. The cell can have a lid that can be removed to view/inspect the "fuel" and ill probably fab one with a removable top lid/access panel to allow for easy cleaning. I think being able to clean and inspect the tank is important in case something goes wrong with the mix. I wont put biodiesel in my stock tanks, although im sure many many people do it. Thats just me though.

 

[Hydro-idi]

This is good information to know. Somewhat off topic but still good to know. I have a local source of B20 and have been contemplating running my idi on it. From what I have heard, it offers excellent lubricity to our rotary pump injection system. Still on the fence on whether or not I should try it out. The alcohol content is what makes me uneasy. But then again, these engines will run on damn near anything

 

[nj_m715]

Don't worry about alcohol. The alcohol is distilled out and reused by any big producer. Some backyard guys will leave it in because they don't have the equipment to pull it back out. BioD does have a cleansing property to it. It can start to disolve and break loose gunk that has settled and built up in our old tanks and lines. You might find yourself changing fuel filters pretty often for the first few tanks.

Here's a plastic front tank. I got one installed about 6 months ago. No problems so far.
http://shop.broncograveyard.com/Side-Mount-Tank-19-Gallon-1985-96/productinfo/30336/

 

[DOE-SST]

IME, POR-15 has been crap. It peels and flakes when exposed to sunlight, so it has to be covered in another paint, and it scratches, abrades and chips easily. Before anyone accuses me of improper prep work, I have been applying industrial and aerospace coatings for 20+ years. I follow the instructions to the letter.

As for something that DOES work, many business aircraft with integral fuel tanks (jet fuel) have the tank structure coated with MIL-PRF-23377K, a 2-part zinc epoxy polyamide paint that wears like iron. I use it on all sorts of parts that will remain outside or receive lots of wear, like hand tools. There are several versions, denoted by different suffix letters, and the most recent is "K", but previous versions work just as well. It is a bit nasty to breathe so a respirator is mandatory. It applies easily and dries to a hard gloss finish. It can withstand the flexing of thin aluminum parts during 4-5G maneuvers and hard landings. Like many aerospace coatings, you need to follow the instructions carefully, to get the best performance from it.