Fuel Tanks

[sunchaser]

Unfortunately, no. In the marine industry, bare aluminum is just left that way. These days, alodine is being outlawed as a dangerous substance. Bare 5000 series hulls are common in salt water though, and don't have rapid corrosion problems under normal circumstances.

For most Al builds great care is taken to ensure dissimilar metals are not in contact with one another. For instance, steel hulls with Al topsides have many protection techniques where Fe and Al are in near contact.

 

[Taras]

As mentioned in Steve D's Tank Design article, "Fiberglass tanks last forever".
Why not have them built in Fiberglass, then you'll be "done" and you won't have to worry about them ever leaking or failing?
Not sure about the cost difference, but maybe worth it......

 

[Comodave]

We had a 540 gallon fiberglass tank built for a previous boat. They cut out the rusting steel tank. Made a form out of 1x2s and then made a mold. Laid up the tank and then cut the back end of the cabin out to slide the tan into the boat. Then glass up the cut and repaint the cockpit. It was a lot of work. Of course we sold the boat shortly after.

 

[mvweebles]

I made this very decision - aluminum vs fiberglass. In Mexico, same price. Materials are expensive, labor is cheap. Aluminum is less labor but materials are expensive even in Mexico. Fiberglass - materials cheap but labor intensive. I read the same Steve D article and chose fiberglass. Fabrication was $6k for a pair of 225g tanks, plus another $1k for fittings and such that I wanted glassed-in vs fasteners. So I'm into my tanks about $7k, maybe more. Including install (engine removal not included because it was out for other reasons)

I would do the same all over again, but I don't think there are many craftsmen in the US making replacement tanks in fiberglass. Welding a metal tank is much faster so no one does it for replacement tanks.

Peter

 

[rslifkin]

Fiberglass tanks can be very nice for anything other than gasoline (even with epoxy there are issues with ethanol compatibility). Fiberglass tanks can easily be made to better use a weird shape and optionally can be integral with the hull. Not sure I'd go integral for fuel tanks, but I did build an integral fiberglass water tank in my boat.

 

[Martin J]

Definelty got junk in the tank, But the pinholes / galvanic corrosion is another problem. Was the tank grounded?

 

[Propnut]

The tank was properly bonded. I think some compound in the gasket material or the glue that was use to glue the gasket to the inspection cover had a chemical reaction with the aluminum.
I'm currently getting quotes to have two new tanks build. We're still planning the triangle loop from North Carolina up to Canada and back this year, if I can correct this problem in time.

 

[Steve DAntonio]

That's a heartache, I feel for you.

Tank port gaskets should be donut-shaped rather than a disc, I have seen this happen many times. Preferred gasket materials are are Viton and Buna N.

The pitting is very likely from water, it has that look, I have seen aluminum tanks fail in as little as two years because water made its way into the tank through an improperly placed vent fitting. Were you showing any water in filters?

Aluminum tanks should be made from 5000 series aluminum, 5052, 5083, or 5086. If the tanks aren't painted, and they shouldn't be, you may be able to see this printed on the stock material somewhere and it should be shown on the commission tag, although that could be wrong.

Unless the tank builder used the wrong alloy, or if it somehow is off spec, I'm not sure you can hold him responsible. The failed gasket is his fault, and even if the gasket material was incorrect, and that's on him not his supplier, it should have been a donut not a disc (there is a photo of exactly this failure in the linked article) but that didn't cause the corrosion.

More here

https://stevedmarineconsulting.com/wp-content/uploads/2022/11/FuelTanksPt1-193-FINAL.pdf

https://stevedmarineconsulting.com/wp-content/uploads/2022/11/FuelTanks194Pt2-06.pdf

Not practical in your case, but this is the main reason I favor FRP diesel tanks, they are impervious to corrosion, from the inside or outside. I happen to be at the Grand Banks yard in Johor Malaysia now, they only use FRP fuel tanks, which they build in house.

 

[ronobrien]

I would ask what alloy of aluminum was used in the manufacture of the tanks. I am not sure but I think that 5052 is one of the preferred alloys. The pitting is probably from some other metal or something that wasn’t done correctly in the manufacture. Sorry for your problems cause the tanks should have lasted at least 20 years or more.

5052 is the preferred type of aluminum for tanks. If the manufacturer is following ABYC there should be a permanent tag attached to the tanks with material type, gauge, date of MFR and their name. If they used the wrong material for whatever reason some financial adjustment should be due.

 

[ronobrien]

Skimming through the comments I didn't see any mention of PE tanks. Is this a possibility?

 

[Alisske]

I dont think i saw this in the description, but thats crevice erosion. It occurs when saltwater gets trapped between aluminum and a non porous surface.

The water gets trapped and becomes hypersalinated which raises PH and it becomes acidic. (Or something close to that, lol)

I know from personal experience. (Installed a new aluminum tank by an excellent manufacturer. One year later was n area doing work and saw it pitted to hell n contact areas.).

The install can totally effect the tank more than its construction. Alum tanks need epoxy coat and air circulating surrounding them.

Contact points should be sealed on both sides. (I use starboard strips buttered with 4200). Never treated me wring after that

 

[Propnut]

Now for the next issue with building new tanks. I've received quotes from two well known aluminum marine tank fabricators and both said that inspection ports on the side of the tanks do not meet ABYC standards.
Inspection ports on the top of the tanks won't work as the top of the tanks are only 4 " from the floor above. I've owned boats in the past with inspection ports on the side of the tanks that came that way from the factory. Have the rules changed?

 

[Alisske]

Im surprised they wont make them the way you want.

Just odd

 

[Comodave]

For gas tanks that is true. But I thought there was an exception for diesel. Maybe Steve D will weigh in.

 

[rslifkin]

For gas tanks that is true. But I thought there was an exception for diesel. Maybe Steve D will weigh in.

That was my understanding as well. No holes below the top in a gas tank. But no such restriction for diesel.

 

[Propnut]

I hope y'all are correct. I'll check back with both fabricators tomorrow and make sure they know this are diesel tanks.

 

[Comodave]

I hope y'all are correct. I'll check back with both fabricators tomorrow and make sure they know this are diesel tanks.

I found this. Note it says that openings below the top are allowed in diesel tanks.

Fuel Tank openings: Any opening in gasoline fuel tanks must be on the topmost surface of the tank. The fuel inlet, the fuel tank vent, the opening for the level gauge and the opening for the pick up must all be on the topmost surface of the tank.

Prohibited openings: Drains are not allowed. Sight gauges are not allowed.

Diesel tanks are allowed to have openings below the top of the tank such as a drain, or sight gauges.

In a Steve D article I found this.

Aftermarket stainless-steel and aluminum inspection port "kits" are available (see the sidebar on page 102). Remember: plan on installing at least one inspection port in every baffled chamber. Ports can be installed in either the top or the side of a diesel fuel tank; the former is preferred when access permits. Even if you have to move a fuel tank to access its inspection ports, they're still worth having. The alternative is having no access to the inside of the tank under any circumstances.

I would trust Steve D without reserve. I however probably would not trust a tank fabricator that does not know the standards…

 

[Steve DAntonio]

This is actually poultice corrosion, crevice corrosion is unique to stainless steel. Also, if water accumulates inside a tank, it can then support biological life, the byproduct of which is hydrogen sulfide, which is acidic, which can attack the aluminum.

Aluminum corrosion https://stevedmarineconsulting.com/paint-and-aluminum-how-to-ensure-a-good-mix-2/

Air circulation around the outside of the tank is important, to prevent external corrosion. More on fuel tank installations here https://stevedmarineconsulting.com/fuel-tank-installation/
This corrosion issue is, however, internal.

Aluminum tanks actually are fine uncoated, on the outside, in fact that's my preference. If water migrates between a coating and the aluminum, corrosion can actually be worse, again that's poultice corrosion.
More on that here https://stevedmarineconsulting.com/paint-and-aluminum-how-to-ensure-a-good-mix-2/

 

[Propnut]

I received this from Brian Goodwin,Technical Director with ABYC

Inspection openings are permitted in diesel tanks.

From ABYC H-33 Diesel Fuel Systems

33.10.3 If inspection access opening(s) are installed, they shall have a minimum diameter of 4.75 in (120 mm) at suitable position(s) for cleaning and inspection of the lowest part(s) of the tank. The access opening(s) shall remain accessible when the tank has been installed in the craft.

Inspection openings on the side of the tank are not permitted on GASOLINE tanks.

Best regards,
Brian

So why are the fabricators telling me they cannot certify diesel tanks with inspection ports in the side? They said they would build and install ports on the side, but just couldn't certify the tanks.
Has anyone had tanks built lately and run into this issue.
SP Tanks and Speedy Tanks both told me the same thing.

www.abycinc.org

Brian Goodwin
Technical Director
Phone: 410-990-4460 x115
Email: bgoodwin@abycinc.org




-----Original Message-----
From: Don Sasser <ds@nc.rr.com>
Sent: Wednesday, March 15, 2023 8:21 PM
To: Brian Goodwin <bgoodwin@abycinc.org>
S

 

[Insequent]

I received this from Brian Goodwin,Technical Director with ABYC

Inspection openings are permitted in diesel tanks.

From ABYC H-33 Diesel Fuel Systems

33.10.3 If inspection access opening(s) are installed, they shall have a minimum diameter of 4.75 in (120 mm) at suitable position(s) for cleaning and inspection of the lowest part(s) of the tank. The access opening(s) shall remain accessible when the tank has been installed in the craft.

Inspection openings on the side of the tank are not permitted on GASOLINE tanks.

Best regards,
Brian

So why are the fabricators telling me they cannot certify diesel tanks with inspection ports in the side? They said they would build and install ports on the side, but just couldn't certify the tanks.
Has anyone had tanks built lately and run into this issue.
SP Tanks and Speedy Tanks both told me the same thing.

With regard to the section in red, my guess is they think they have a loophole to avoid certifying & guaranteeing their work.

Why would that be? Is there a history of failure for Ally tanks?

Up above someone said in effect no way they would ever have steel tanks. Well, I did replace 30+ yo steel tanks with new steel tanks. No way I'd ever install ally tanks! Steel, with modern coatings and elimination of water ingress to tanks sides (via vertical ER vents without dorades in my case) will be good for the life of the boat.

 

[Comodave]

I would check with some other tank manufacturers. Also I would ask them why they wouldn’t certify the tanks if they meet ABYC standards. Or I would have them build the tanks and certify them and when you get them put the access ports in yourself. They would still meet standards.

 

[rslifkin]

As far as aluminum tank longevity, mine are at 37 years and still going. Full of gas, not diesel, but still. I had the tanks out last year and they looked good everywhere on the outside. What I could see through the fill and sender holes looked good (no inspection ports). I sounded a bunch of places around the tanks with a screwdriver handle and didn't find anything that sounded thin, different, or concerning. So as long as they're mounted well and kept dry, aluminum fuel tanks can last a long time (I've never heard of anyone else having a tank failure on this model boat either).

 

[BruceK]

Have you sent the mfrs the ABYC code, underlining the limitation which only applies to gas tanks, and asked them to respond?
They might say they cannot control what gets put in the tanks after delivery, but that`s your problem, not theirs, if you stipulate you want tanks for diesel fuel only.
This issue likely exists whatever the proposed tank material. As above,I don`t see a problem with steel longevity.
Fitting ports post delivery is an idea, but cutting into the tanks could leave debris you can`t remove which might be deleterious for the aluminum. And affect the mfrs warranty.

 

[Comodave]

Use a hole saw and then clean out the tank before use and you won’t have any problems. You will be cutting into each baffle section so cleanup will be easy enough.

 

[ronobrien]

I would check with some other tank manufacturers. Also I would ask them why they wouldn’t certify the tanks if they meet ABYC standards. Or I would have them build the tanks and certify them and when you get them put the access ports in yourself. They would still meet standards.

You run the risk of giving them another loophole to void warranty. They could say that you altered the tank. Any unrelated defect would not be covered as I am guessing their contract stipulates that ANY alteration voids warranty.

 

[Hippocampus]

As mentioned in Steve D's Tank Design article, "Fiberglass tanks last forever".
Why not have them built in Fiberglass, then you'll be "done" and you won't have to worry about them ever leaking or failing?
Not sure about the cost difference, but maybe worth it......

Agree with this post. Depending upon access would even think of removing baffles from existing tanks and using them as the molds for new grp tanks. Then inserting baffles. Prior boat had 4 fuel and two fresh water tanks integral to the hull. Created in effect a double hull all in grp. Current boat has two saddle tanks in Al but they sit an inch up and one to two inches away from anything so air around them on all side’s except at supports. Underside of supports on gaskets so tanks are isolated.
If I was to do new construction in Al would utilize integral tanks but all internally coated. Probably In epoxy.

 

[twistedtree]

Personally I'd be much more focused on what the contamination is, and where it came from. Then get it all cleaned up and see what the tank condition really is.


Other than the obviously bad gasket material, is there a confirmed fault in the tank or its material. Did the dissolving gasket material actually cause any damage, or just make a mess? It seems likely that the pitting is from water in the fuel, and that will happen again with new tanks, depending on how the water got in in the first place.


Just jumping to replace the tanks for a second time seems to me like an over-reaction.

 

[Hippocampus]

Spot on as usual TT. Have had excellent experience with Atlantic Gasket. They will cut to any size and shape in just about any material. Possibly a custom gasket isn’t required as they have a extensive catalog of prior gaskets they have cut. Needed four gaskets for tank access and and examination ports. Collected orders from sister ships and got an excellent price even though the sets of four were shipped all over the world. Packing was excellent and none creased or damaged.

 

[Nick F]

Personally I'd be much more focused on what the contamination is, and where it came from. Then get it all cleaned up and see what the tank condition really is.


Other than the obviously bad gasket material, is there a confirmed fault in the tank or its material. Did the dissolving gasket material actually cause any damage, or just make a mess? It seems likely that the pitting is from water in the fuel, and that will happen again with new tanks, depending on how the water got in in the first place.


Just jumping to replace the tanks for a second time seems to me like an over-reaction.

+1 !

 

[Mako]

So they used neoprene gaskets instead of cork?