The Offshore Voyaging Reference Site

Q&A: Can I Use Bronze Sea Cocks In An Aluminum Boat?

Question: Do you have bronze sea cocks in your aluminum hull and if so what level of corrosive activity have you seen?

Answer: We have bronze sea cocks insulated from the hull with fiber spacers. The through hulls are plastic. There is no sign of any corrosion around most of the sea cocks, which are located in the engine room. The only exception are the head sea cocks located forward. Here the hull plate under them is showing some light pitting from copper salts dripping off the sea cocks over the last 20 years. I think the reason that the engine room sea cocks don’t have this problem is that the heat from the engine and generator keep them and the surrounding area pretty dry, whereas up forward the area is often wet from condensation, particularly when we are in cold water areas (most of the time).

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Patrick Piret

Dear John ,

We are building a new 50 ft sailyacht based on a Dijkstra plan but finishing in another yard as their usual builders . I have one question to you ;
Fuel tanks are incorporated in the hull and coated to prevent MIC corrosion . The fuel lines are of copper pipe which we insulated in plastic pipe and the valves are brass insulated with the white thread teflon tape .
Is this also what you have on your boat and is this common practice ? What is the alternative for copper and brass fittings for this ?