Aluminum versus stainless steel fuel tanks

[svfinlandia]

I am in the process of replacing one of the stainless steel fuel tanks on my Nauticat.
I had planned on replacing it with another stainless steel tank, but the yard that is doing the work said that and aluminum tank would be better, so I had the tank made from aluminum, but after seeing the finished product and I wish I had gone with stainless steel.
Difference in weight was not an issue since the aluminum tank had to be thicker than the stainless steel and the difference in weight would have been minimal.
Also, I now find that the aluminum tanks will have to be coated with something to keep them from corroding.
Any thoughts from the group hours which would have been the better material to make the tags from and why?

Al, S/v Finlandia

[roverhi]

Stainless or aluminum, if they sit in saltwater or ofte wet from saltwater will corrode. Had ss tank develop pin hole leaks after 4 years. Keep the tanks bottoms dry and they’ll last.

Replaced a monel tank with aluminum after the solder joints on the monel tank began to leak in multiple places. Sanded the tank, undercoated with zinc chromate and painted with enamel paint. Still looks good after 6 years but it stays nice and dry.

[JPA Cate]

We had an aluminum diesel fuel tank made for our previous boat. It eventually got a pinhole leak in it in its lowest corner, where any condensation would have gone. We were somewhere way out away from services when we discovered it, and Jim epoxied a bit of beer can over it, and the leak quit and we never did anything else with it. The beer can had been good for around 8 years, at the time we sold the boat.

Sorry, don't know whether or not there is a "better" in this situation. But the beer can repair was fast and easy.

Ann

[a64pilot]

Plastic is best in my opinion, followed maybe by fiberglass.
Monel or Titanium would be good I guess, but likely way more expensive.
Knocking on wood, my aluminum tanks are 32 yrs old, yes they will fail of course, it’s only a matter of time, but isn’t 32 yrs likely longer than you will need them?

[coopec43]

Originally Posted by a64pilot

Plastic is best in my opinion, followed maybe by fiberglass.
Monel or Titanium would be good I guess, but likely way more expensive.
Knocking on wood, my aluminum tanks are 32 yrs old, yes they will fail of course, it’s only a matter of time, but isn’t 32 yrs likely longer than you will need them?

I wonder why you are replacing a ss tank. Maybe it work hardened because of continual flexing as the fuel sloshed around the tank and that started a leak?

https://www.boatdesign.net/threads/s...l-tanks.33681/

Diesel tank. Aluminum or Stainless?

https://www.thehulltruth.com/boating...anyone-ss.html

[RaymondR]

Welded 1/2" black poly.

[billknny]

Had an aluminum tank in my last boat. No corrosion, inside or out, no issues at all and it was 40 years old. It sat high and dry on the after bulkhead in the engine room above any possible water contact.

Diesel is not corrosive to either material. If either one sits in water, especially salt water, you will have a problem in fairly short order. If you have water inside the tank, you have all kinds of nasty problems. If your boat leaks water, FIX IT!

[Singularity]

Agreed polyethylene (basically limited to Moeller in the US) or build your own fiberglass.

Why? Resale vs piece of mind? More tolerant of external exposure to water? I'm sure that plastic diesel tank horror stories exist, but you don't hear about them much. Seems like half of the people like steel, half like aluminum, neither half wants to admit that plastic exists (enter comments about the lack of baffling in a PE tank).

Moeller:
https://www.easternmarine.com/Moelle...oat-Fuel-Tanks

DIY fiberglass:
https://www.practical-sailor.com/new...glasstanks.pdf
https://www.thehulltruth.com/boating...n-project.html

[blubaju]

20 years gre (glasfiber w epoxy), I am retired stainless steel fabricator.

[coopec43]

Do polypropylene tanks meet the ISO standards?


B2 FUEL TANKS
The construction of permanently installed fuel tanks must meet the requirements of ISO 21487 or ISO 10088 and their installation must comply with ISO 10088.
Portable fuel tanks must meet the requirements of AS 2906.


ISO21487 Commercial Craft
https://www.sis.se/api/document/preview/915498/


ISO 21487 and ABYC H33 Fuel tank fire & Static pressure test - TPR2

www.tpr2.com/certs/boat_fuel_cell_report_F1ES.pdf
Jan 26, 2011 - For installation requirements, ISO 10088 applies.‖. -International Standard ISO 21487, First Edition 2006-12-15. Small Craft – Permanently ...


http://www.tpr2.com/certs/boat_fuel_...eport_F1ES.pdf

[coopec43]

I suppose you have to be careful that the particular polypropylene tank conforms to the appropriate standards.
(As Singularity states above " Moeller in the US")

[RaymondR]

You can have as many baffles as you want in a fabricated welded poly tank.

[nhschneider]

I remember reading that ABYC only approves of stainless steel fuel tanks if they’re cylindrical in shape with rounded ends. That being said, when our 90-gallon starboard stainless steel fuel tank developed a leak after being in service for 20 years, we replaced both port and starboard tanks with stainless steel ones. I would have preferred going with roto-molded ones but couldn’t find the size I needed.

Fair winds and calm seas.

[SV Sailfish]

Originally Posted by JPA Cate

Jim epoxied a bit of beer can over it, and the leak quit and we never did anything else with it. The beer can had been good for around 8 years, at the time we sold the boat.

Best use of an empty beer can ever! Love it!!

[Gaia]

We replaced two ss tanks on GAIA because of crevice corrosion at the welds in spite of having passivated the welds with nitric acid on the inside.. If any water enters the tank, and condensation is difficult to prevent, corrosion will occur due to a lack of oxygen.

We replaced the tanks with rotomolded polypropylene 20 years ago. End of issues. SS, particularly 304 or even so called 316 from countries with lax quality control which pay lip service to the low carbon designation, is not the wonder material we sometimes think, particularly in the marine environment.

Jim