Concrete bilge corrosion

[RCardozo]

I own a 73' Dutch Sailing Barge with a rivetted iron hull built in 1893. The outside of the hull is fiberglassed. The bilge was concreted about 10 years ago and was bone dry until about 1 year ago. A crack developed in the fiberglass and a small leak has let sea water into the bilge. It is permeating thru the concrete. There is evidence of corrosion taking place but I think that is at the water air barrier. The steel in the bilge is coated with coal tar epoxy. Any ideas on what kind of corrosion is taking place in the saturated concrete? Once I fix the leak what should I do to the bilge? The concrete will dry out and I assume alot of salt will be left in the concrete. Can I flush the salt out or do something to mitigate the effects of the past salt water intrusion?
Prior to the leak the hull was sound and finished w/ coat tar epoxy then concreted. Any corrosion should be the result of this one leak.

[balsaboatmodels]

Yeow! that's an issue.

Umm, if it were my boat, I'd be paranoid about water also percolating between the iron and fibreglass outside and between iron and epoxy inside.

Water in those situations is like gophers in a golf course - you just can't tell what it's getting under and where it'll pop up, until it does.

Now, how to check that without either much expense going the high tech route, or hard work tearing layers apart and then much expense repairing the "archaeological dig" so to speak, well . . .

Sorry I can't tell you anything of a more definitive nature.
:-/
FSW

[timgoz]

RCardozo,

In years of study on steel boats & construction I've never heard of glassing over steel or iron hulls.

There is a reason for the above, especially with riveted iron. Sad to say, but I feel, IMHO, you will have more & more trouble as time progresses. There may be much more present damage not yet visble.

Add the concrete ballast & you have a potential for a huge "rust sandwich".

Personally I would not put much money into the vessel without some serious, very professional, on site evaluation.

Take care.

TGoz

[Mikey]

If I remember right, then the corrosion itself gets 5 times the size of the original iron that it corrodes. One of the reasons a ferro cement hull can be unsound while it still looks pretty sound. Wouldn't matter in your case, I suppose.

I believe in flushing out the salt, then leave it (for weeks) to dry it out completely before sealing.

Mikey