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Old 06-25-2018, 07:57 AM   #1
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Anode Mixture

This 4th O' July long weekend on boat I plan to put on new anodes for each shaft, both rudders, big "license plate" bonding system between trim tabs and on trim tabs them selves. Recently I put new pencil zinks into engine cooling systems.

Our boat is exclusively in fresh water.

Here's my question:

What is wrong with [i.e. is it detrimental to anode or diode metals] to mix different kinds of anode metals attached to diode metals for hopefully maximum corrosion determent?

In other words... What is outcome if I put a Zinc, and Magnesium / or Zinc and Aluminum / or, all three anodes on the shafts - with Magnesium in all other anode locations???

It's not that I'm experiencing corrosion trouble at all - just wondering about anode mix on the shafts... seeing as I'll be under boat playing around with anode replacements anyway!

Input always appreciated!!

Thanks - Art
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Old 06-25-2018, 10:00 AM   #2
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Never mix anode metals.
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Old 06-25-2018, 10:25 AM   #3
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Zinc is near worthless in fresh water. If you can find all magnesium, that would be best. All aluminum next best. Certainly wouldn't mix anode metals that were bonded together.

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Old 06-25-2018, 11:03 AM   #4
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The most anodic one will stay anodic and waste. The least anodic ones will go cathodic and will get plated. Ones in the engine do not have enough of a conductive path through the hoses for them to affect anything outside, especially in FW.
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Old 06-25-2018, 11:47 AM   #5
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Is it worth looking for aluminum anodes for engines for boating periodically in fresh/salt water? I didnít find any on boatzincs.com.
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Old 06-25-2018, 07:26 PM   #6
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Quote:
Originally Posted by Ski in NC View Post
Ones in the engine do not have enough of a conductive path through the hoses for them to affect anything outside, especially in FW.
I had to think about this. Do you mean that the water path between the motor and exterior anodes is long enough to not cause problems with dissimilar anodes?
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Old 06-25-2018, 07:40 PM   #7
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Is it worth looking for aluminum anodes for engines for boating periodically in fresh/salt water? I didnít find any on boatzincs.com.
If you are looking for alum pencils try Go2Marine.com

It seems strange BoatZincs.com carries alum shaft, rudder, etc but not pencils but I also looked and turned to Go2Marine for mine.
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Old 06-25-2018, 07:41 PM   #8
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If you are looking for alum pencils try Go2Marine.com

It seems strange BoatZincs.com carries alum shaft, rudder, etc but not pencils but I also looked and turned to Go2Marine for mine.
Thanks, Don.
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Old 06-25-2018, 07:57 PM   #9
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Thanks everyone... I plan to go all Magnesium!
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Old 06-25-2018, 09:07 PM   #10
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I had to think about this. Do you mean that the water path between the motor and exterior anodes is long enough to not cause problems with dissimilar anodes?
Yes. too low conductivity through the water in the length of hose. Each engine cooler can be considered separate from stuff outside of boat.

You want your sacrificial anode to be more anodic on the chart than any of the alloying agents in the metals to be protected.

I'm not sure what is motivating going with different anode alloys unless the rate of wastage is unnecessarily high. I'd figure the strongest anode would offer the best protection.

I've studied a lot in galvanic corrosion, but lots of gaps in my knowledge base.
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