Engine Anodes and Freshwater Flushing

[firehoser75]

I have been freshwater flushing my engine and generator (Cummins 6BTA and Onan) since I have owned the boat (4 years now), including leaving freshwater with a mixture of “Salt Away” in over the winter (no freeze issue here).
Steve D’Antonio, on another forum, has recently stated that once a zinc anode is immersed in freshwater it forms a coating and will no longer function properly without being taken out and cleaned off.
I have not been doing this, and have recently noticed a bit of corrosion starting on the outside of both heat exchangers (engine and generator). My zincs seem to last a very long time as well. The aftercooler was off 2 years ago, and had no issues.
How best to continue freshwater flushing, but ensure my anodes “do their job”? I understand that aluminum anodes might be the best answer, but are not available for engine anodes??? Someone suggested using magnesium anodes, but checking on them often. I have lately drained the water after flushing (using the lower anode on the aftercooler), but don’t know if the zinc “coating” is already happening?
What is considered the “best practise”?
Thanks,
Tom

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[firehoser75]

Thanks Tony.
I will definitely keep up the freshwater flushing. I am a bit unclear why my external HX corrosion can be from my ER environment. I use a Wolverine oil pan heater (all winter and whenever at dock in summer). In the winter I run a dehumidifier (in the boat with hatches open) as well, and the ER humidity never exceeds 60% and temps never go below about 50 degrees F. Summer is warmer temps, and about the same or a bit more humidity. I posted a general ER photo to give an idea of what my 2002 Cummins looks like. The engine HX corrosion is where the end cap meets the HX just beside the anode. Someone PMed me and informed me of where I can source aluminum pencil anodes. Would that be a good idea, or stick with zinc as you first suggested?
Thanks,
Tom

[Tony Athens]

My answer–

Tell Steve D’A to pound sand, and you, keep fresh water flushing.

100% –stay away from “SaltAway” if you are fresh water flushing or operate in fresh water. Complete waste of $$ and time

Stay with zincs anodes

External “corrosion” has nothing to do with what you are asking–This is a DIRECT RESULT of the “atmosphere” inside your engine room when your boat sits at the dock–It has zero to do with zincs, etc etc etc.

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David R Flamer, Mike Uliasz

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