Alum Fuel Tanks dont' last forever, check often

[flyingfin]

Hard to believe that this 2002 boat needed a new tank after only 17 years,,,,,but at least the manufacturer designed it with a removable hatch so it did not cost the owner another couple thou$and bucks to cut the deck open!

Like any other marine equipment, you need to monitor all components constantly for corrosion,,,,,,out of sight out of mind does not work. Bare aluminum is a problem, a rubber wrap, annodized finish or plain old coal tar epoxy coating might have helped it last a little longer,,,,,,,or it was just to thin and poor quality aluminium to begin with?

Watch at 6:30 to see who built the boat, then how weak the remainder of the tank was

https://www.youtube.com/watch?v=qwywa-JJ-Xc

[CSY Man]

Nice video, I learned something.

[boatpoker]

Originally Posted by flyingfin

Bare aluminum is a problem, a rubber wrap, annodized finish or plain old coal tar epoxy coating might have helped it last a little longer

Tens of thousands of aluminum boat owners and this Certified Marine Corrosion tech will disagree with you.

The problem with aluminum fuel tanks as shown in the video is complete disregard of proper installation. This is no different than the common corrosion of improperly installed steel fuel tanks which Taiwan is famous for. Simply following ABYC or ABS tandards for metal fuel tanks would ensure these tanks would last for many, many decades.

[Celestialsailor]

Generally aluminum fuel tanks fail four ways...


1) Either made too thin or poor welding.
2) Prolonged chafe in one area.
3) Sitting in either salt water or even fresh water.
4) Through condensation or water entry through a vent, water accumulates at the lowest point of the tank and if it is never removed, will corrode from the inside out. This is how my tank failed..no way to remove accumulated water inside the tank.


I have a 1977 Westsail 28 and I have just built a new aluminum tank for it. I made a lot of design changes. 1) Increase material thickness from .093" to .125".

2) Change the shape to conform more closely to the hull shape, increasing fuel capacity.
3) Rubber carpet all edges to insure chafe protection.
4) Bend the bottom seam...not weld.
5) I saddled the tank 1/2" off the hull and bottom and foamed in a few areas to allow air flow and not allow water build up anywhere.
6) Added a 3/8"NPT port to siphon water out of the lowest point of the tank.


Personally, I would not use an aluminum tank in a bilge. In the video you can see holes in the top of the tank. This was probably caused by salt water sitting on top of the tank. I would have built an epoxy fiberglass tank for that application.

[Orion Jim]

My factory original aluminum diesel tank lasted 25 years. It had developed pin holes where it was in contact with a painted plywood shelf. I placed four strips of Treadmaster athwartships on the plywood shelf, about 2” wide, to ensure there is an airspace and a way for moisture to escape from under the base of the tank.

[coopec43]

I used contact cement to attach rubber strips to the tank. The rubber strips then sit on the "floors" which I hope sorts out any corrosion problems.

[rslifkin]

Originally Posted by Orion Jim

My factory original aluminum diesel tank lasted 25 years. It had developed pin holes where it was in contact with a painted plywood shelf. I placed four strips of Treadmaster athwartships on the plywood shelf, about 2” wide, to ensure there is an airspace and a way for moisture to escape from under the base of the tank.

The strips are a good idea. The mounting for my 35 year old aluminum fuel tanks is similar, and as far as I can tell, the tanks are still in good shape.

[gonesail]

even rubber strips can hold moisture and corrosion. 17 years is definitely enough time for a tank to fail. the best you can hope for is not having to cut the boat up to replace it. also foaming in a tank is old school and not recommended IMHO.

[HopCar]

The reason the tank in the video failed is that it was foamed in place. This used to be a common practice but it held moisture next to the tank and caused corrosion. I don’t think any boat builder does that anymore. You need to let some air to circulate around the tank as much as possible.

[Scott Berg]

I've seen alloy tanks last 30 years and fail in 10; often it's the bugs that live on the line between water and fuel at the bottom of the tank. On my own boat the day tank (hanging, not on supports below) just began to weep diesel; it's 44 years old and, as it draws from the bottom (gravity feed) it wasn't the usual culprits. We'll take it out next week, get a good look inside, and repair (weld a new bottom) or replace. Aluminum isn't forever, even good aluminum that is properly cared for, but you should see 30-40 years from a well made, well installed tank. Shout out to John Gallo of Atlantic Coastal Welding who makes most of the tanks for my marine business; good work and very good customer service; no relationship with them other than very happy customer...

[Celestialsailor]

Originally Posted by gonesail

even rubber strips can hold moisture and corrosion. 17 years is definitely enough time for a tank to fail. the best you can hope for is not having to cut the boat up to replace it. also foaming in a tank is old school and not recommended IMHO.

I have been hearing that foam is not recommended since the 80's but whenever I ask for proof, it's always secondhand and never any tangible evidence. Usually it's "A surveyor told me". I'm not saying that it can't happen because theoretically it can if you're not careful. Never foam in an area where water can accumulate. But this would be true if you used chocks and water sat between the chocks and the tank. It is out the utmost importance to keep air flow around the tank to evaporate moisture or allow small amounts of water to flow away.

Originally Posted by HopCar

The reason the tank in the video failed is that it was foamed in place. This used to be a common practice but it held moisture next to the tank and caused corrosion. I don’t think any boat builder does that anymore. You need to let some air to circulate around the tank as much as possible.

The reason that tank failed was because it was in the lowest part of the boat where water sits and yes the foam kept it there. That tank should have been fiberglass, not aluminum. I find it odd how they think because the new tank is powder coated that it will remedy the future event of a failure...it won't. It will eventually give way also.

[Cheechako]

Fuel tanks almost always fail either on a weld, or more often right where the tank sits on a support. It gets wet in there between the metal and the support and corrodes fast.
My '86 boat was corroded through by '92, 6 years for a SS tank. My trawler tanks were aluminum and corroded/leaked.

It can be a big expense and is something to always look for in a used boat. It may require interior to be torn out for tank access.

[Rotten Ricky]

The continued use of aluminum fuel tanks just amazes me. Yet people just swallow what the aluminum and boat-building industries find convenient and good for sales. Even in the face of common sense and failures.

After also suffering from the disaster that an aluminum tank made in my boat, I looked at alternatives. I had one professionally built of fibre-glass and it is so superior. Consider that it:

- will not corrode inside or out - even with the metal straps that secure it outside.
- is easier to custom form to the hull or other shape - no metal sheets have to be used and no dubious welding occurs. Welding can negatively affect metal.
- increases tankage because it takes advantage of above hull and other restricting nearby surfaces.
- will last ... almost forever - gas-station, in-ground fuel tanks have at least a 50-year warranty! This tells you something!
- resists spark development for explosion that can happen with metal tanks - fibre-glass will not conduct the needed electrical charge.
- is accepted by insurance and boat-building industries.
- are easily and safely built by most handy people.
- when professionally made, mine still cost 60% of a simple inferior "suitcase"-styled aluminum tank!

Yet for years now, I have watched as aluminum fuel tanks continue to be fitted and there is frequent failure from interior or exterior moisture. This is not rocket science!

The "suitcase-shaped" tank in my boat was replaced by one that increased tankage by about 70% and it is now over 40 years old and is still in perfect shape. So I suggest that you find a company that builds tanks for industry (these guys build tanks for acids and the nastiest liquids on the planet - so they know their stuff!) and they will be happy to oblige your easy request. Provide a mock-up of the tank needed. The builder of mine laughed when I asked about a warranty - and gave me a lifetime warranty!

Note - gasoline will attack common polyester resin and so vinylester is used on the interior surface. Diesel is not a problem for either. Also, it is common to give a rinse coating of epoxy to guarantee that any tiny fibres cannot be present.

They will install baffles inside to prevent violent movement of fuel. I am a great believer in safety, redundancy and being prepared - it takes very little more money and provides similar baffled effect by building two smaller tanks that are joined by hoses and valves - that also provides isolation of fuel in case of contamination and often makes it easier to install, etc.

It is also easy to build water tanks (coat the interior with food-grade epoxy for no taste issues) and waste tanks of fibre-glass. I built my rugged and custom-shaped holding tank - and nothing is more dangerous than those contents!!

Cheers - and keep safe everyone! Yes - virally or politically!

[Monte Cresto]

The largest problem I've seen with Aluminum Tanks are electronic fuel gauges. While
in Santa Barbara I met a Charter Boat Owner having to replace his AL tank (only after
a few years) on a Valiant 40 due to the electrical current from his fuel gauge. I quickly
removed mine on my 1978 Downeast and it is still like new. I've been using a wooden
stick ever since.

[Cheechako]

Originally Posted by Monte Cresto

The largest problem I've seen with Aluminum Tanks are electronic fuel gauges. While
in Santa Barbara I met a Charter Boat Owner having to replace his AL tank (only after
a few years) on a Valiant 40 due to the electrical current from his fuel gauge. I quickly
removed mine on my 1978 Downeast and it is still like new. I've been using a wooden
stick ever since.

Yeah those gauges are often not working anyway. I've replaced those with the mechanical direct reading gauge which gives you decent idea what the level is. (reads right on the tank top and goes right on where the electrical sender was attached)