Black Iron Fuel Tanks

Anyone know about black iron fuel tanks on a CHB? Good, bad, ugly?
Thanks, James

My Marine Trader has two 250 gallon black iron tanks installed when she was built in 1978. So far, so good. No leaks, no problems...knock wood!

The success of black iron fuel tanks on boats depends entirely upon the installation techniques and maintenance. Even though we call them "black iron" they are really sheet steel, about the thickness of a car body. But they are not usually painted like a car body.

They corrode (rust) due to two principle causes: water running down the filler hose and sitting on the top of the tank and bilge water accumulating on the bottom. The first is readily fixable by making sure that the caulk around the fill fitting is sound.

The second is tougher and can't be easily fixed. Boat builders often set the tanks on a plywood platform or set them on a bed of foam (which is worse). The foam collects water which lets it eat away at the steel.

The only solution to a foam installed tank is to pull the tank, chip out the foam and buld a base of wood stringers and supports so that bottom is open and can drain. For a plywood mounted tank it is sometimes possible to lift it and work stringers under it to let it ventilate.

So while your tanks are still good, take a look at making them last much longer.

If you have to replace them, then reinstall them right, or better yet, make them out of SS.

David

David,
Any idea why they called them "black iron"? I've wondered about that for years. I replaced my black iron tanks w aluminum 8 years ago. Perhaps they painted them black and didn't want to use the word steel as everyone knows how fast steel rusts. My aluminum tanks have a rough black finish. "Black iron" sounds like not a finish but a special kind of iron made for the purpose. So I've always thought "black iron" was meant to be as misleading as possible.

manyboats said:

Any idea why they called them "black iron"? I've wondered about that for years.

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HRPO steel (Hot Rolled Pickled & Oiled) is what they used to call Black Iron Plate back in the day. It has a natural black patina from the heating and cooling, but isn't anything special. Just mild steel.

I wouldn't use stainless though. It's subject to hydrogen embritlement and the flexing of a boat can actually make the fail sooner. If mine ever fail, I'll be replacing with Aluminum tanks.

Thanks SS it's more ligit than I though.

I had SS tanks in my last boat and they didn't give trouble but hearing about the SS welds I chose aluminum for Willy.

I replaced my leaking 15 year old steel tanks with aluminum tanks over 17 years ago. No worries.

djmarchand said:

The success of black iron fuel tanks on boats depends entirely upon the installation techniques and maintenance. ...They corrode (rust) due to two principle causes: water running down the filler hose and sitting on the top of the tank and bilge water accumulating on the bottom. The first is readily fixable by making sure that the caulk around the fill fitting is sound.

The second is tougher and can't be easily fixed. Boat builders often set the tanks on a plywood platform or set them on a bed of foam (which is worse). The foam collects water which lets it eat away at the steel...David

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We replaced the steel tanks in our last boat after 16 years for the exact reason you mentioned. The builder had used foam to support the tanks with minimal drainage. Other than the areas of the tank that were in contact with the foam, the tanks looked great.

Our current boat has steel tanks that are 26 years old and so far so good. Talking to other owners of the same make, it appears that most of the tank failures have been from the inside which in my opinion is preventable.

Larry M said:

We replaced the steel tanks in our last boat after 16 years for the exact reason you mentioned. The builder had used foam to support the tanks with minimal drainage. Other than the areas of the tank that were in contact with the foam, the tanks looked great.

Our current boat has steel tanks that are 26 years old and so far so good. Talking to other owners of the same make, it appears that most of the tank failures have been from the inside which in my opinion is preventable.

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That's why a boat with good fiberglass tanks, like the Hatteras's will never give you a problem. Don't rust, deteriorate, and are perfect for diesel fuel.

Then what are the disadvantages of fibreglass tanks?

Especially on a boat like mine in which the steel is curved to conform to the rounded hull.

jnvoss said:

Anyone know about black iron fuel tanks on a CHB? Good, bad, ugly?
Thanks, James

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Get a flash light. Look at the tops of the tanks. Do you see water or evidence that water had been running down fittings and sitting on top of the tank? If the tanks have very little exterior rust and you maintain the boat, then they will probably last a heck of a lot longer (decades). Most tank failures on CHB/Taiwan Trawlers are from the outside in due to rust deteriorating the outside of the tank, eventually eating through the thin layer of steel.

I am unaware of CHB's ever being built on top of foam. Also, CHB tanks are usually well above the bilge, most likely the bottom of the tanks will never see water creeping up from the bilge, so again, fittings and screw holes in the teak deck are the usual cause of failure. Get your flash light out and inspect the top of the tanks yourself.

Just cut out my mild steel tanks that had bubbling rust just about all over them...especially where water got under the insulation glued to the tank.

Though after cutting them out...they looked like they would have lasted another 10 years at least with no maintenance at all they were so thick.

But I am much happier now that I can see through my poly tanks, I don't have 2" of sludge on the bottom any more, working around them is so much easier and I halved the space taken up by the tanks so I really improved engine room layout and storage.

The downside is I reduced my cruising range to around 300NM instead of having 1200NM....I can live with that because of the other advantages.

psneeld said:

The downside is I reduced my cruising range to around 300NM instead of having 1200NM....I can live with that because of the other advantages.

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Great trade off IMO the overwhelming majority of these boats are way over tanked considering their actual usage.

Yeah, if I ever re-tanked mine I'd certainly drop the fuel quantity. I have 600 gallons now that would take weeks to burn off even at 8 hours of cruising a day.

psneeld said:

Just cut out my mild steel tanks that had bubbling rust just about all over them...especially where water got under the insulation glued to the tank.

Though after cutting them out...they looked like they would have lasted another 10 years at least with no maintenance at all they were so thick.

But I am much happier now that I can see through my poly tanks, I don't have 2" of sludge on the bottom any more, working around them is so much easier and I halved the space taken up by the tanks so I really improved engine room layout and storage.

The downside is I reduced my cruising range to around 300NM instead of having 1200NM....I can live with that because of the other advantages.

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Would really like to hear more about this and photos of your project would be great.........

Wxx3 said:

Then what are the disadvantages of fibreglass tanks?

Especially on a boat like mine in which the steel is curved to conform to the rounded hull.

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Not a lot, except I understand they don't like biodiesel - it eats into them apparently. However, if I had to replace my tanks, which are stainless steel, I would go for smaller volume fuel grade plastic, like psneeld. Then they can be made to shape, are light and easy (relatively) to install, and are corrosion proof to just about everything you could expose them to.
I replaced my water tanks with those, and it was a breeze...

rochepoint said:

Would really like to hear more about this and photos of your project would be great.........

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Not much to it....cut them out with a recip saw...took several days per tank as I could only cut about two feet or so before the saw would get hot. I'd let it cool before cutting again. I burned up a 30 year old cheapo saw about 1/2 way through the first tank s I went easy on the new one case I liked it...

If I had really gone for it...I could have had the tanks out in a day..2 guys with 2 great but disposable saws...a day for sure.

Built ledges out of plywood for the new ones to sit on as well as relocating batts and tools, spare parts, etc up on them so i'll have NO clutter around the engine any more.

I was sure the new thanks would just slide right in...wrong by an inch...I did have to temporarily remove one floor support each side to get the tanks in....knuckleheaded builders blind ring nailed the supports to the engine room flooring so after carefully unbolting the supports...I still had to sledge hammer and cut nails with the metal saw blade. I really dislike production boats!!!!!!!!

Still in the process of replumbing, made a manifold for the eng/genset...nothing exotic.

The only thing yet unresolved is the vents on the new 58 Gal Moeller (off the shelf for $329 per) poly fuel tanks are 5/8 and the old vents are 1.0 inch. Because they are vents...not too worried I'll rig something easy.

First photo just shows the edge of the tank and how little rust penetration there was...I forgot to measure the thickness but guess it at around 3/16...probably the strongest thing on the whole Albin.

Second photo is the sludge on the bottom of my tanks...that was after a 2000 mile trip with running on some pretty sloppy days and no filter clogs (hardly anything even in the filters) and the fuel in the sight tubes ALWAYS looked pristine.

Here's the supply and return manifolds awaiting lines...

Fiberglass tanks are built for any type of diesel fuel as long as they are built properly. The reason you don't see many is because they are very costly to build. Most good builders are starting to use them, example is Selene yachts.

Ditto

I was afraid of the old tanks until I climbed in and inspected the tops of al the tanks which looked great. Tap on them if you want. They are much thicker than you think. I have read a lot of failures are due to top rust, caused by leaky teak decks.

Adelaide said:

Get a flash light. Look at the tops of the tanks. Do you see water or evidence that water had been running down fittings and sitting on top of the tank? If the tanks have very little exterior rust and you maintain the boat, then they will probably last a heck of a lot longer (decades). Most tank failures on CHB/Taiwan Trawlers are from the outside in due to rust deteriorating the outside of the tank, eventually eating through the thin layer of steel.

I am unaware of CHB's ever being built on top of foam. Also, CHB tanks are usually well above the bilge, most likely the bottom of the tanks will never see water creeping up from the bilge, so again, fittings and screw holes in the teak deck are the usual cause of failure. Get your flash light out and inspect the top of the tanks yourself.

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