Why no zinc

[George Kornreich]

Apparantly some engines (closed system fresh weter cooled with heat exchanges) such as my volvo MD22L have no zinc. Is this wise? If so, I wonder what makes them "immune" to galvanic corrosion to the point that the manufacturer chose not to install zincs? (On my Kohler genset, using a Yanmar engine with a similar closed cooling system/interchanger there IS a zinc. Strange???)ThanksGeorge Kornreich

 

[Dave Ullrich]

Shaft Zink!

Your genset must have a zink on it because it does not have a shaft with a zink. You main engine should have a shaft zink on it. Since there is a metal to metal connection all the way from the engine to the shaft zink, it should be well protected from galvanic corosion by the shaft zink.

 

[Eric Lorgus]

Fresh water Yanmars don't have zincs either

Geroge: The GM series of Yanmars that are direct sea water cooled (i.e., no heat exchanger) do have engine zincs, while the fresh water cooled (with heat exchangers) do not. My guess is that since the fresh water cooled engines are never in direct contact with sea water, there is no need for a sacrificial zinc.I think the reason for a zinc on the prop shaft is to attract galvanic corrosion from the other (more expensive) metal parts that are below the water line. Why your fresh-water cooled genset has a zinc might have to do with the electrical currents that the genset itself is generating.