Tag Archives: corrosion

Sacrificial anode

The anode on the propeller shaft wears out in two seasons. We also had a problem with corrosion of the heat exchanger (a new one was provided by Vetus under warranty) and corrosion of the ball valve on the sea water intake for the engine.

To hopefully avoid premature death of our new engine and other fittings, we have fitted a small pen anode in the sea water circuit of the engine as well as a 5 kg anode on the hull, wired into the engine. Let’s see what happens…

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As close to the propeller and sea water intake as possible, with a free line of sight to both.

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Bronze thru hull post connects the zinc anode to the 16 mm2 tinned copper wire from the engine

Replace heat exchanger

During the three seasons since new, the heat exchanger has developed small corrosion pits at the front cap for the tube stack. The tube stack itself and the inside of the heat exchanger were fine. To their credit, Vetus sent a complete new heat exchanger without any discussion whatsoever. It looks slightly different from the original one.
The o-rings for the end caps are 61×2.5. The end caps of the new heat exchanger are brass instead of the original plastic.

As with most new engines, it does not have any sacrificial zincs. All the manufacturers claim that the alloy shall withstand corrosion. Well, I’ve fitted zincs anyway…

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Old heat exchanger

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New heat exchanger

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New. Aft end cap.

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New. Fwd end cap.

Old. Corrosion of housing at o-ring.

Old. Corrosion of housing at o-ring.