Aluminum/Zinc Anodes

[jlombardo]

Aluminum/Zinc Anodes

I have a 1998 Mainship 31 Sedan Bridge. Unfortunately, this boat did not come with internal strainers on the raw water intake. I have the boat out of the water for the winter and besides replacing the manifolds/elbows, I am installing strainers. Now that I will have internal strainers, my thought is that I will flush the raw water side of the cooling system with fresh water if the boat is going to sit for a week or more. Afte doing some reading it was suggested that zinc anodes (the type I currently use) will not work after being in fresh water and that I should switch the motor anodes to aluminum.

This brings up several questions and is the reason for this thread.

1.) Is there a value in flushing the raw water side of the cooling system?
2.) Which is better for saltwater use, zinc or aluminum?
3.) If I change the anodes in the heat exchangers to aluminum, do I need to change all anodes to aluminum. This boat does have an internal grounding system, so all metal is technically connected. I use anodes on the rudders, shafts, and heat exchangers.

Any advice would be greatly appreciated.

John

 

[Captain_Michael]

The running gear sits in salt water. Stay with zinc. There was a recent thread on this forum about fresh water flushing after every use. Worth reading. Consensus was that it probably helped moderate corrision. But again, most of the water flowing through raw water strainers will be salt water, so I would continue to use zinc anodes.

 

[Comodave]

I disagree since aluminum anodes are good for any water while zinc anodes are only good for saltwater. If you are going to freshwater flush then the zinc anodes will develop a coating on them and become ineffective. You can use different anodes inside the engines and the outside of the hull since they are effectively different bodies of water. But since aluminum are good everywhere I would just go with all aluminum anodes for everything. I use aluminum on the hull and magnesium inside the engines since I couldn’t find aluminum in the size I needed, I didn’t look very hard though, so I just went with magnesium since I am in freshwater, but magnesium is only good in freshwater so it won’t work where you are.

 

[Bacchus]

I agree w Dave. For alternating fresh & salt water or brackish conditions ALUM us recommended.
Look at the Perfirmance Metals website for more info & a great selection of pencil anodes. I posted links in the other anode thread if interested.

 

[O C Diver]

I would also go with aluminum on all anodes. I spend about 5 months in fresh, about 5 months in brackish, and maybe a 2 in salt. Much simpler to go with aluminum that works in all. While it may take a little looking, all anodes for our boats are now available in aluminum.

Ted

 

[BBS]

Does performance metals sell retail to individuals? I was led to believe they sold to business accounts.

 

[O C Diver]

Does performance metals sell retail to individuals? I was led to believe they sold to business accounts.

I buy from them directly. Nobody in my area carries there products. I usually do $100 to $200 order to make it worth their while. They really need to open an Amazon store and sell at retail to protect their stocking dealers.

Ted

 

[jlombardo]

I do appreciate everyone's input and will be switching to all Aluminum.

Thanks!

John

 

[Bacchus]

Does performance metals sell retail to individuals? I was led to believe they sold to business accounts.

I called them to ask and when they checked my zip code they indicated they did not have a retailer nearby. I've ordered a couple times and they sent them w/o issue.

 

[Steve DAntonio]

Late to the game but I would second the use of aluminum anodes. However, I have had some cases where aluminum pencils develop a frothy coating, which had no effect on their performance (tested with a ref cell), however, it can make them difficult to remove. Therefore, if you go with aluminum pencils, initially check them monthly to ensure you don't have this issue.

I'm also an advocate of fresh water flushing.

 

[Comodave]

I had a problem from last summers anodes. When I unscrewed the brass plug the anode came unscrewed from the plug and stayed in the aftercooler and in the heat exchanger. One was of course the most, almost impossible, anode to get to. I would have had to remove the aftercooler which was a bear to do. I took the brass plug and ground the outside threads off and ground the plug down to a much smaller OD. Then carefully screwed it back onto the aluminum anode. Then I was able to pull it out of the aftercooler. So on the new anodes for this summer I used blue Locktite on the aluminum anode and screwd it back into the brass plug. I measured the resistance before and after using the Locktite and couldn’t see any difference. I will see what happens after this season.

 

[fstbttms]

Which is better for saltwater use, zinc or aluminum?

Same same, all samey same. Either are fine and there is no appreciable difference in performance.

 

[rslifkin]

Late to the game but I would second the use of aluminum anodes. However, I have had some cases where aluminum pencils develop a frothy coating, which had no effect on their performance (tested with a ref cell), however, it can make them difficult to remove. Therefore, if you go with aluminum pencils, initially check them monthly to ensure you don't have this issue.

I'm also an advocate of fresh water flushing.

I regularly get that frothy buildup on my trim tab anodes (aluminum in fresh water). None of my others seem to do it, so it may just be an issue of low water flow across the top of the trim tabs.

 

[Insequent]

I had a problem from last summers anodes. When I unscrewed the brass plug the anode came unscrewed from the plug and stayed in the aftercooler and in the heat exchanger. One was of course the most, almost impossible, anode to get to. I would have had to remove the aftercooler which was a bear to do. I took the brass plug and ground the outside threads off and ground the plug down to a much smaller OD. Then carefully screwed it back onto the aluminum anode. Then I was able to pull it out of the aftercooler. So on the new anodes for this summer I used blue Locktite on the aluminum anode and screwd it back into the brass plug. I measured the resistance before and after using the Locktite and couldn’t see any difference. I will see what happens after this season.

I was surprised to read that you use brass plugs with aluminium anodes. Somewhere recently I read that you had to use stainless plugs with aluminium anodes. I'd be interested in hearing more about this configuration.

 

[Comodave]

I was surprised to read that you use brass plugs with aluminium anodes. Somewhere recently I read that you had to use stainless plugs with aluminium anodes. I'd be interested in hearing more about this configuration.

Not sure exactly what they are, I just said brass…

 

[HeadedToTexas]

I believe my anodes are all magnesium. The rudder anode is clearly much further gone than the transom anodes. And the swim platform anodes are much further gone than the prop shaft anode. The higher sacrifice rate is due to the larger nearby surface area of metal, so that all makes sense.

 

[Bacchus]

I believe my anodes are all magnesium. The rudder anode is clearly much further gone than the transom anodes. And the swim platform anodes are much further gone than the prop shaft anode. The higher sacrifice rate is due to the larger nearby surface area of metal, so that all makes sense.

What are you using for engine / cooler pencil anodes?
When I was switching after moving to freshwater I could not find a full compliment of Mag pencils and went 100% to Alum..

 

[HeadedToTexas]

I'll figure that out, Don. This will be my first pencil anode replacement. Seaboard Marine's guide to Cummins "zincs" is somewhat less than clear. Are there not just three?

https://www.sbmar.com/articles/zinc-locations-for-the-mechanical-b-c-qsb-5-9-qsl-wet-qsm-engines/

 

[Bacchus]

Vince
I can't help w a. Cummins as mine is Yanmar.
I would thoroughly investigate all coolers... raw/coolant, oil cooler, after (air) cooler and tranny cooler.
Some of mine have 2 others just 1 anode. Some tranny coolers have none.
Important to look all around and pull anything that looks like a plug or anode to be sure.

From my research using all the same anode material is recommended for hull & running gear but engine coolers can be different, if necessary, as they are remote and the separation makes them a separate "cell" that's not affected by the hull anodes.

 

[HeadedToTexas]

Thanks Don. I haven't found magnesium pencil anodes yet. The search is on.

 

[fstbttms]

Thanks Don. I haven't found magnesium pencil anodes yet. The search is on.

https://boatzincs.com/categories/magnesium-anodes/engine-anodes/replacement.html