Not THOSE zincs...

[RT Firefly]

Greetings,
From what I understand, folks with zinc anodes (hull, rudder prop shaft) would be best to change to magnesium anodes if boating solely in fresh water and aluminum if going back and forth. Correct me if I'm wrong but this is NOT the question. What about the zinc anodes in heat exchangers? Same deal? Are anodes for these devices available in mg or al?
I seem to remember a recommendation of renewing one's zinc anodes after spending some time in fresh water and then returning to salt because of a layer of ?? that develops in FW and renders the anode inert. Should the HE anodes be replaced as well?
I'm sure the answer is obvious but going through a period of brain farts at the moment.
Thanks.

 

[Alaskan Sea-Duction]

Good question RT as I am going from fresh to salt, then back again. I seem to recall someone telling me to buy the Canadian made anodes...

 

[THD]

Mr RT-the manual for a Krogen does state that anodes need to be changed from zinc to either magnesium (fresh water) or aluminum (brackish water) and also states that the engine zincs do not need to be changed. No explanation as to why and I certainly have no clue.

 

[obthomas]

Its complicated: http://www.boatzincs.com/pdfs/Chart_B-Which_Anodes_Should_I_Use.pdf

 

[obthomas]

RT

You once explained to me how electrolysis works. If you have forgotten let me refresh your memory:

 

[Alaskan Sea-Duction]

Now that is funny!!!

 

[obthomas]

Once you understand these things its easy.

 

[Bacchus]

RTF
I moved my MS to fresh water and replaced ALL of the zincs w/ AL after doing a fair amount of research.
My findings - Mg is the "best" eg provides the most protection in fresh water but have a short life. I could not find replacements for all of my "zincs" in Mg. AL is recommended for brackish and is second best for fresh (and provides longer life than Mg).
The recommendations include changing ALL anodes that are bonded together... which to my thinking should include engine anodes - which I also replaced w/ Al.
Side Power sells only Zn & Al anodes for their thrusters but informed me that mixing is not a problem as their thrusters are electrically isolated and do not interact w/ other bonded underwater metals.

After 2 seasons my observations are that the Al are functioning - wearing away - and I see no adverse effects on underwater metal.
Also - I have seen other boater that mixed Zn & Al and the Al is reacting / wearing while the Zn show NO sign of activity - which is what I'd expect from the info I read - Zn builds up a surface oxide layer that prevents reactivity.

 

[RT Firefly]

Greetings,
Mr. ASD. Curses, hoisted on my own petard....

Thanks all. What generated the question is that we WERE in fresh/brackish and I never changed over from zn to mg or al as we frequently made forays into salt but I've been doing my regular zinc check and sort of went hmmmm....

 

[Bacchus]

In that case...

You might want to wire brush vigorously to remove the oxide layer and return the original Zn reactivity in salt water.

 

[RT Firefly]

Greetings,
Mr. B. Good plan. I'll ask the diver to do so if there's still GOOD life in the existing anodes. ANY sign of wastage and I'll replace.