Copper diesel tank. Why not?

Mary51 · #1 02-02-2008

I recently read that there's a problem with having a copper diesel tank. Figured the p.o. had a good reason for having one, because he had a good reason for pretty much everything else he did.

Is this really a problem? I have a 25 gallon tank and just filled up today for the fourth time in the three years I've owned the boat. Haven't had any fuel problems (knock wood!).

Mary

lharmon · #2 02-02-2008

Mary51;

I know of no problems using copper tanks. I do know there are regulations for the minimum thickness of the copper walls of your tank - possibly about 14 gauge if my memory serves. My 1981 sailboat has a small copper tank that has been serving us and it well for many years.

With the price of copper and the price of fuel, our tanks are becoming more valuable each season.

Hopefully nobody knows of any problems with these tanks. I suspect they are pricey and that their are more economical options.

LH

camaraderie · #3 02-03-2008

Copper corrodes in a salt water environment ...it is a problem waiting to happen...but if you've got one...just keep an eye on it...particularly the fitting areas and the parts you can't see that are in contact with the hull. I might put a coat of epoxy on it to protect from oxidation.

Lancer28 · #4 02-03-2008

I helped a friend with a copper tank recently - here is what he did

We started with draining, removing and cleaning it. After plugging the outlets and filler neck, we used copper abrasive pads (chore-boy?) after sanding it lightly on the outside to remove the oxidation.

After that, it was just ever so lightly rough to the touch. We applied 3 coats of epoxy to the outside and reinstalled, which stuck nicely to the freshly roughed surface.

It seems like it will be as tough as any other tank over time. The only thing I would see as a problem now is getting corrosion inside the tank.

sailboy21 · #5 02-03-2008

Quote:

Originally Posted by camaraderie

Copper corrodes in a salt water environment ...it is a problem waiting to happen...but if you've got one...just keep an eye on it...particularly the fitting areas and the parts you can't see that are in contact with the hull. I might put a coat of epoxy on it to protect from oxidation.

What doesn't corrode in a saltwater environment?? Sheesh!
Can't be any worse of a risk than steel, aluminum or stainless tanks. Just keep it clean and don't let anything damp, wet or metallic come in contact with the tank surface.

Didn't they use copper to clad the bottoms of wood ships? There are some copper components topside on my boat that seem to be doing well. There are swages and chain guard on my sprit.. both copper and I don't know how old.

camaraderie · #6 02-03-2008

SB... Right...and the pennies in my pocket don't seem to be wasting away either BUT...Copper is REALLY active corrosion wise when compared with annodized aluminmum, galvanized steel and fiberglass...all "normal" tank components.
Copper clad bottoms are in an anaerobic environment. I am thinking of tanks sitting in the bilge of the boat and subject to both salt and moisture and oxygen...A copper day tank to feed a heater etc. is probably no issue at all. But...I can tell you what the copper stripping from my ssb ground plane looks like in those same bilge places in pretty short order. Not saying to get rid of them...just saying to take steps to 1)inspect 2)preserve. The penny under my mast doesn't look too good!

sailboy21 · #7 02-03-2008

Quote:

Originally Posted by camaraderie

The penny under my mast doesn't look too good!

Oh no! The first time I took down my mast I found an antique silver coin (1793). It was in fine shape, however it was sitting in a hole about 1/4" deep in places it had created in the cast aluminum mast step!!! I didn't want to bring bad luck on my vessel, so I replaced it with a silver coin of a little lesser value, but put in a little zip lock bag first

Back to the fuel tanks, but correct me if I am wrong that a metal tank in boat should never be in a position where it is constantly exposed/submerged in bilge water unless it is built in to the hull.

camaraderie · #8 02-03-2008

SB...correct...but leaks and moisture get trapped in the bilges as does condensation and especially in areas where there is not good air circulation, this enhances corrosion on any metal tanks. Same reason we coat bottoms of floorboards in epoxy...keep the moisture out.

artbyjody · #9 02-03-2008

Quote:

Originally Posted by sailboy21

Oh no! The first time I took down my mast I found an antique silver coin (1793). It was in fine shape, however it was sitting in a hole about 1/4" deep in places it had created in the cast aluminum mast step!!! I didn't want to bring bad luck on my vessel, so I replaced it with a silver coin of a little lesser value, but put in a little zip lock bag first

Back to the fuel tanks, but correct me if I am wrong that a metal tank in boat should never be in a position where it is constantly exposed/submerged in bilge water unless it is built in to the hull.

[Cam] - is your copper ground plate sheathed in Epoxy...? I was under the impression that is how it was done less it was a retrofitted deal?

[original poster]

As for the fuel tank - it really is dependent on the type of copper nickle (CuNi) ratio of the alloy used (its not a pure copper tank) as well as thickness. The oxidation is usually a protective barrier and unless not a proper ratio - usually will never cause a issue with the interior and the exterior can just be lightly scrubbed from time to time to freshen up the protective layer ...There is really no cause of alarm in most cases when dealing with copper tanks exposed in the bilge if proper maintenance is taken...

To give you more info on the subject I recommend reading:

http://www.copper.org/applications/c...er_topics.html

hellosailor · #10 02-03-2008

As I recall, the sulphur content used as lubricant in diesel fuels causes sever pinholing in copper tanks and lines. And pressurized copper lines are forbidden, because they work harden then fail anyway.

Diesel is now "low sulphur" compared to what it used to be--at least in the US and EU, IIRC, so perhaps copper won't fail as badly as it used to.

But I'm fairly certain the sulphur content was the problem, and that was why copper tanks were considered doomed from day one.