Aluminum Anodes?

[bawlmer]

Fellow Sailors. The last time I purchased a prop shaft anode was in 2015 and it was zinc. As I go through my pre splash punchlist I went to my West Marine store to purchase a new prop shaft anode. I was informed by the WM guy that they only sell aluminum anodes, no more zinc. He said it was for the benefit of the bay as way too much magnesium was being deposited by zinc anodes. Is this a Peoples Republic of Maryland thing? Is aluminum less effective than zinc? Google says you can still buy zinc anodes. I am all about saving the bay but definitely not at the expense of my metals. I have no issue with returning the anode and buying a zinc elsewhere. What say you?

 

[dlochner]

The current thinking is Magnesium or Aluminum for fresh water, Aluminum for brackish water, Aluminum or Zinc for salt water.

A significant issue for zinc in fresh or brackish water is that it forms a hard coating that effectively insulates the zinc from the water, thereby offering no protection. Aluminum does not have this problem.

Check Boatzincs.com for more info and good prices.

 

[JamesG161]

He said it was for the benefit of the bay as way too much magnesium was being deposited by zinc anodes

Say What?
So WM [clerk] thinks depositing Magnesium is Bad, from a Zinc sacrificial Anode?

But it is ok to deposit Aluminum.

OMG...
If you DON'T uses an anode you deposit IRON!!!!!

My local WestMarine Store will deliver any on-line product to their store [I pick up] or directly to me.

I have to admit, the last time I swam in the Chesapeake Bay, it was Salt Water [ closer to Annapolis ]
Get you money back, write WestMarine why and go to where dlochner said...
Jim...

PS: To change the Element Zinc to the Element Magnesium would take splitting the Atom.

 

[Gunni]

Cadmium, not magnesium. Cadmium is a toxic metal that bioaccumulates...you’ll end up eating it. Cadmium is a common contaminate of smelted zinc.

You will get better cathodic protection in the bay and the ocean with aluminum. Been using it for years.

 

[thinwater]

In fact, in brackish water, like most of the Chesapeake Bay, they are more resistant to scaling and perform better. I did a bunch of testing for an article, based in Deale, MD. It is actually an aluminum alloy with a potential very similar to zinc.

No, it is not a MD DNR rule, it is because they work better in this area.

 

[bawlmer]

Ok. I sail in the upper bay so the water is brackish, definitely less salty than Deale and probably a little less than Annapolis. The argument for aluminum looks solid. I will be installing the aluminum anode. The one warning I did receive was to make sure all of my anodes are one type. I have another anode in my heat exchanger. I need to check that to see what it is. I recently purchased it from WM so it may also be aluminum. You do learn something new every day. Thanks everyone for your wisdom.

 

[JamesG161]

The one warning I did receive was to make sure all of my anodes are one type

Not really a problem, but best to match. Aluminum can "protect" your Zinc.
Jim...

 

[thinwater]

In theory, the anodes should all be the same alloy. In practice, if you have a zinc in the engine and aluminum on the shaft, they are far enough apart that it is not serious. But in the future, go with one alloy.

How brackish the water is in the marina depends as much on the creek as it does on where you are in the Bay. The harbor can be nearly fresh if there is a lot of flow. In Deale, the two creeks are quite different (one is longer and has more flow).

 

[jssailem]

Aluminum can "protect" your Zinc.
Jim...

@bawlmer It is the chart man.. the chart.

Not the insight or blind sight of the WM sales team...

High School Chemistry...

• “Electrochemical corrosion of metals occurs when electrons from atoms at the surface of the metal are transferred to a suitable electron acceptor or depolarizer. Water must be present to serve as a medium for the transport of ions.”

It is kind of like the story of Roots...

“In a sense, corrosion can be viewed as the spontaneous return of metals to their ores;”​

 

[All U Get]

Maybe that’s why an outboard never deteriorates? Surely too much rum.

All U Get

 

[jibes138]

Buy your anodes right here on SBO. Great anodes at fair prices.

 

[bawlmer]

I try to patronize SBO whenever possible. Functional fixedness steered me toward WM.
As far as the water in the inner harbor goes, fresh may be a bit of a stretch.

 

[jssailem]

Steve... From the read I have done on the Baltimore Harbor, Fresh and Water are words that are found in a dictionary but not in the Harbor.

 

[dlochner]

Buy your anodes right here on SBO. Great anodes at fair prices.

After reading this I went off to the SBO store to buy my anodes, unfortunately they do not carry (or at least I couldn't find them) aluminum anodes for my MaxProp. I'd gladly order them from SBO and even pay a buck or so more to support the site, but ordering anodes from 2 different sources doubles the shipping and I give enough money to UPS, they don't need more.

 

[jssailem]

Dave... give @Dave Groshong a call.

 

[JamesG161]

they are far enough apart that it is not serious

The Aluminum and Zinc anodes must be "Electrically" connected.

So I mentioned...

Aluminum can "protect" your Zinc.

I have a Zinc in my Genset, which is NOT, electrically Connected to my Shaft Zinc.
Therefore, they sacrifice at different rates.
_____
We berth in Brackish and sail in Salt Water. I never worry about my Zinc anodes.
I test my protection every 6 months with...

http://www.boatzincs.com/corrosion-reference-electrode.html

This bought me "peace of mind" for all my "metals" exposed, including my Lead/Antimony keel.
Jim...

PS: SBO store did not show one.
PSS: I still change my anodes , now about every 9 months. As tested and proven.
PSSS: This probe can detect Stray currents in your marina, also.

 

[Tally Ho]

I also was used to zinc, but when I purchased a new anode last year, my local chandlery said Magnesium for fresh water. I am on Lake Michigan. The anode shows deterioration, maybe more than an old style zinc. I bought a second one to add to the shaft before I splash.

I was surprised by how much it cost compared to a zinc anode.

I don’t see magnesium shaft anodes on the SBO site :-(

Greg

 

[dlochner]

I also was used to zinc, but when I purchased a new anode last year, my local chandlery said Magnesium for fresh water. I am on Lake Michigan. The anode shows deterioration, maybe more than an old style zinc. I bought a second one to add to the shaft before I splash.

I was surprised by how much it cost compared to a zinc anode.

I don’t see magnesium shaft anodes on the SBO site :-(

Greg

Here's a link to some of them on SBO: https://shop.sailboatowners.com/prod.php?12457

Yes the Magnesium and aluminum anodes may cost a bit more, but at least they work.

 

[Alec]

I've been using aluminum anodes on my shaft & heat exchanger for past three years. Last summer I noticed my engine running somewhat hotter at higher rpms. When I removed the old aluminum anode it was well wasted but covered with a clear jelly like substance. I removed the exchanger for a good cleaning & when I removed the end caps the end near the anode was full of a thick paste & jelly surrounding the anode. The anode seemed to have had a good electrical connection so now I'm not sure if I want another one.
Alec

 

[Dalliance]

The last time I bought shaft anodes, I ordered a three year supply at no increase in shipping cost over a single anode. I use magnesium for fresh water and they are surprisingly light weight. Hold a zinc anode in one hand and a magnesium anode in the other, and it’s real easy to tell them apart even though they look the same to my eye.
I used Boatzincs.com and was very satisfied, but will check this site first the next time I order.