Aluminium diesel tank with bronze elbo and copper pick up tube. Corrosion potential?

[Scout 30]

Originally Posted by boatpoker

Many aluminum boat owners will be surprised by this statement.

Good point! How about, if your aluminum tank will be exposed to saltwater be sure to install zincs.

[Bill Seal]

For gasket material, go to an auto parts store and get the cork/neoprene stuff like is used for pan and valve cover gaskets. Rubber just squeezes out.

[a64pilot]

Originally Posted by Jim Cate

One wonders how aluminium hulls last so long, considering that they float in saltwater full time.

Jim

In all honesty it is hard to understand that and to correlate it with the fact that aluminum fresh water tanks rot out, and aluminum black water tanks especially fast, apparently even fuel tanks.
I don’t think anodes is the answer, but don’t know what is.
Is all corrosion actually an electrical thing? Can you protect from chemical corrosion with an anode?

As near as I can tell my tanks remain clean and dry on the outside unless there is condensation on the outside. I have not seen that, but this last Winter I fought condensation inside of the boat, so I can see how it’s possible under the right conditions.

[Eastward ho 24]

I originally had the karropak gasket stuff From the auto parts store was to thin for my application. I thought rubber would do just fine. Next time I inspect the tanks I'll use the buna stuff which I assume is fancy rubbver

[Jim Cate]

In all honesty it is hard to understand that and to correlate it with the fact that aluminum fresh water tanks rot out, and aluminum black water tanks especially fast, apparently even fuel tanks.
I

One possible explanation is that the tanks are not made from the same 5000 series alloys that hulls typically use. I know that the aluminium diesel tank that I had made for our previous boat was from a 6000 series alloy. It developed a pinhole leak in a weld after a decade or so which I repaired with epoxy, and was still in non-leaking use when we sold the boat at 17 years age. BUT, it looked like crap on the outside!

Jim