Galvanic Corrosion

[ejay]

I recently installed the temperature alarm system on my raw water cooling circuit. The alarm system has brass fittings connected to the engine, but then someone advised me I should never have brass on the engine due to risk of galvanic corrosion. Is this correct?

[joe_db]

I recently installed the temperature alarm system on my raw water cooling circuit. The alarm system has brass fittings connected to the engine, but then someone advised me I should never have brass on the engine due to risk of galvanic corrosion. Is this correct?

Sort of. Bronze is better, but plenty of fittings just don't come in bronze. Practically I have yet to see an issue with my brass fittings on the engine.

[hanleyclifford]

A brass sensor on a block or head is usually not a problem since it usually just carries a wire. A brass nipple OTOH carrying coolant and supporting a hose is subject to vibration and angular moment. It takes many years for a brass connection in a block carrying antifreeze for an electrolyte to develop a problem, but brass carrying salt water into an iron block is a big no no.

[ndutton]

The more you understand galvanic corrosion the better you'll be able to manage it. This treatment is about the best I've seen on the subject and as Joe said earlier, speaking from practical experience I've never had a galvanic problem with brass or brass content alloys on any marine engine I've been involved with over 50+ years.

[ejay]

The temp sensor fitting would not be a problem I guess, however I do have brass water fittings coming into the water pump. What metal is the MMI water pump? Is there risk of corrosion there?

[hanleyclifford]

The temp sensor fitting would not be a problem I guess, however I do have brass water fittings coming into the water pump. What metal is the MMI water pump? Is there risk of corrosion there?

The MMI pumps are bronze or red brass; I'm not sure. In any case yellow brass is fine in the pumps. The real issue is problems in the expensive castings (head, block, manifold) that are not easy to remove for repair. Anything can be re drilled, tapped etc - we just don't want to be in a position to have to do it in a remote anchorage. Good idea to have NPT taps and appropriate drill bits when cruising.