Anodes Aluminum Fresh water

Blueone

Blueone

Well-Known Member
SILVER Sponsor
Jan 24, 2007
13,830
Lake Erie, Ohio
Boat Info
2004 420 Sundancer
Engines
Cummins 6CTA 450's
I was in storage yesterday and a friend stopped by and noticed I have magnesium anodes. He said he switched years ago to aluminum…. He is around the corner from me in the same water…. He says they work great. I knew about aluminum but it never crossed my mind to switch.
What’s everyone’s opinion on aluminum in freshwater?
Reason I ask is if aluminum works as well …. I can make my own and the size I want.
I have a lot of different grades of aluminum at the shop. What I found online is they have a lot of zinc in the aluminum. But I can’t find a grade….. does anyone know?

A40B783F-F628-4E38-ADF3-B81A2D108D84.jpeg
 
What I found in doing all of the research on getting my boat balanced is the aluminum for anodes is alloyed to MIL-DTL-247790. As far as I can tell, that is the only anode alloy. It is classified as a "low voltage" aluminum. The use of a structural aluminum like 6061 or 5051 or 7075 would probably not give the results desired. The 3xxx and 5xxx series are for marine use so definitely couldn't be used for anodes.
 
Aluminum in fresh water really depends on location. In my area, if you use aluminum on a bravo 3 by end of season you will have bubbled paint everywhere on the lower unit.
I would not risk making your own. The mix of materials to get it to the correct noble level would be tricky.
 
paulswagelock said:
Aluminum in fresh water really depends on location. In my area, if you use aluminum on a bravo 3 by end of season you will have bubbled paint everywhere on the lower unit.
I would not risk making your own. The mix of materials to get it to the correct noble level would be tricky.
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No doubt - aluminum on aluminum no bueno. Magnesium based anode would be the only choice to protect aluminum.
 
Blue, I have been using aluminum in Lake Erie since my first boat that didn’t involve outdrives, so that would have been the 360 in 2008. I switched back to zinc for the pencil anodes though after less than desirable results with them in salt water (they would stick in the cases) If you are staying strictly in the Great Lakes, as others have said, performance Metals makes the aluminum pencil anodes and they work well in the hx, ac, and gear cooler.
I wouldn’t make them. Just buy them, then you know.
 
Blueone said:
I was in storage yesterday and a friend stopped by and noticed I have magnesium anodes. He said he switched years ago to aluminum…. He is around the corner from me in the same water…. He says they work great. I knew about aluminum but it never crossed my mind to switch.
What’s everyone’s opinion on aluminum in freshwater?
Reason I ask is if aluminum works as well …. I can make my own and the size I want.
I have a lot of different grades of aluminum at the shop. What I found online is they have a lot of zinc in the aluminum. But I can’t find a grade….. does anyone know?

View attachment 142663
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I just ordered some trough of all places Walmart. They actually came from a marine supplier. They were the cheapest even after shipping. When I ordered them I checked off fresh water, and for Bravo 1. So I’m assuming they are made from the right material. They looked to be pretty complete kit as well.
D24346D5-8F28-48F5-8299-6E45EE6E9E98.jpeg
 
ttmott said:
What I found in doing all of the research on getting my boat balanced is the aluminum for anodes is alloyed to MIL-DTL-247790. As far as I can tell, that is the only anode alloy. It is classified as a "low voltage" aluminum. The use of a structural aluminum like 6061 or 5051 or 7075 would probably not give the results desired. The 3xxx and 5xxx series are for marine use so definitely couldn't be used for anodes.
Click to expand...
I saw that too but the spec doesn’t say grade.
 
bbwhitejr said:
Check out Performance Metals and their Navalloy Aluminum Anodes. I have been running them on my 3rd boat now in FW and they perform great!

https://performancemetals.com/pages/navalloy-aluminum-anodes

Bennett
Click to expand...

Navalloy® anodes are made to the military specification MIL-DTL-24779B(SH) and contains approximately 95% aluminuum, 5% zinc, 0.02% indium and less than 0.3% of other trace elements. The alloy is cadmium free.

I’m asking my supplier if they carry it…. Thanks
 
Thanks guys….. I thought if I could make some fancy anodes out of scrap aluminum in the shop it might be worth the effort….. Navaloy seems to be the material but my supplier doesn’t carry it. So that idea is done. I bought magnesium anodes from boat zincs for $100….. problem solved
 
Regarding the mention of pencil anodes getting stuck and or breaking, this is a classic problem of traditional, zincs that are threaded to the internal plug cavities. REDZn Engine Anodes prevent this from happening with a new plug design that acts as a puller (no threads, no torque that causes breakage). Makes changing the anodes as simple and boring of a job as it appears to be. Been a game changer for me on my boat (I am enthusiastic user and designer). They're currently available in zinc. Regardless, as others have pointed out, 'aluminum' is not 'aluminum'. Don't make your own from scrap as it must be milspec material - Al is gaining in popularity though zinc is still dominant by far. Also, you can use Zn in your motors and Al on your running gear (or vice/versa), but don't mix in the same spot.


my3sons said:
Blue, I have been using aluminum in Lake Erie since my first boat that didn’t involve outdrives, so that would have been the 360 in 2008. I switched back to zinc for the pencil anodes though after less than desirable results with them in salt water (they would stick in the cases) If you are staying strictly in the Great Lakes, as others have said, performance Metals makes the aluminum pencil anodes and they work well in the hx, ac, and gear cooler.
I wouldn’t make them. Just buy them, then you know.
Click to expand...
 
I love it when you fresh water, Great Lakes, guys get "caught"....:cool:
 
CapeNIslands said:
Regardless, as others have pointed out, 'aluminum' is not 'aluminum'. Don't make your own from scrap as it must be milspec material - .
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Do you guys read above posts?….. there is a mil spec …it’s useless in telling what grade that meets the spec. It tells you what the grade should contain. My original post was asking for a grade that would meet the mil spec.
I was hoping scrap aluminum in the shop would meet the spec….. no where close so the idea is done…. I bought Mg
 
Blueone said:
Do you guys read above posts?….. there is a mil spec …it’s useless in telling what grade that meets the spec. It tells you what the grade should contain. My original post was asking for a grade that would meet the mil spec.
I was hoping scrap aluminum in the shop would meet the spec….. no where close so the idea is done…. I bought Mg
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Your "original post" was about opinion on aluminum in fresh water and using scrap aluminum that was laying around. Another poster alluded to the Mil standard and that the chemistries were quite different from commercial structural aluminum. If you look at the ASTM standard B221 for example and see exactly the chemical composition for the 6xxx alloys you can compare to the MIL standard and see exactly what the differences are. There may be an obscure cast aluminum specification that is close to the MIL standard but for common 3xxx, 5xxx, 6xxx, and 7xxx alloys that are typical for commercial uses there is no compatibility.
 
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