Cauliflower-like material on underwater anodes

[baz]

I've noticed that my trim tab anodes get a heavy coating of a cauliflower-like material after a few months of being replaced. My understanding is that this type of coating will in fact stop the anode from doing its job. For this reason I've tried at times to remove this material with a strong long handle wire brush. It kind of comes off but much of the coating remains.

This coating occurs well before the trim tab anodes have eroded to around 50% so I'm a bit ticked off that I'm not getting the full value of having the anodes.

As an aside, I also note this same kind of material collects and coats our Yanmar 4BY2-150 engine anodes so my thoughts are they don't get their full life span for protecting the engine's innards.

Am I correct in thinking this cauliflower-like material is stopping the anodes from doing their work ? If so, has anyone any thoughts on how to avoid the anodes from being covered with this kind of material so that the full life span of the anode can be realized ?

Thanks... 🙂

 

[abcandjrc]

I don't have an answer for you, but it might help others to answer if you specify whether you are in fresh or salt water, and of what material the anodes are made. There are so many choices now, that perhaps you have a water/material mismatch.

Zinc was the only choice until a few years ago but now aluminum, magnesium, and probably exotic alloys of any and all of those are on the market. It could make a difference. (One reason I think it would help is that I have never seen anything like that on "zincs" in either fresh or salt water.)

 

[knotflying]

Hey Barry, you may have something going here, fresh vegetables while cruising! Personally, I prefer broccoli. :lol:

 

[kskogerson]

I believe you are looking at a normal process. This is what the anodes do. I wouldn't remove the "oxidation" as this would only expose fresh zinc so that the process would accelerate. My two cents.
Kent

 

[LADYBUG TOO]

Most oxides behave like ceramics so the effect is to insulate the anode from its surroundings. I would expect the condition to be more prevalent in salt water as it occurs on our R-29 anodes and we do remove it to make sure we have conductivity. Since the anode is "sacrificial" we want to keep it that way. Depending on how long Ladybug, Too is on shore power we find that anode deterioration is higher the longer we are connected. After reducing our connection time we found that we get longer anode life. Also, the lightning strike we had came through our shore power system so we never leave it on long anymore.

Pat & Carolyn, Ladybug, Too

 

[baz]

More info to help with the discussion...

Anode material is Alu.
Boat kept in salt water all year round.
When boat is docked it's under cover and is stern in with very little direct sunlight hitting the trim tabs.
When boat docked it's always on shore power.
Shore power cord is the SmartPlug model.
When docked the Refrigerator is set to #2 and a WM De-humidifier is always on.
Diver service for the underwater anodes is performed every 4 months.
The boat is equipped with a transom mounted zinc anode attached to the engine's bonding system via a prop shaft brush.
The boat is equipped with a Galvanic Isolator.
The swim step bracing struts have donut zinc anodes at their base (only partial submerged when docked).
The prop and thruster anodes are Alu.
Other boats nearby in our Dock also have this same cauliflower-like look covering their underwater anodes.

I will be asking my Diver service about this as they perform anode service for hundreds of boats in our PNW area.

Now that I think about it, this cauliflower-like substance on the trim tab anodes has only been observed since switching from a Marinco shore power cord to the new fancy SmartPlug shore power cord.... Hmmmm, maybe the SmartPlug is being very smart at producing fresh vegetables as Mike Ruuso has jokingly alluded to. :lol:

 

[HRowland]

From the Boatzincs.com FAQ page:

The hard scale commonly found on the surface of zinc anodes is Zinc Carbonate (ZnCO3). Carbonate (CO3) occurs in all bodies of water and originates from atmospheric carbon dioxide gas (CO2) naturally dissolving into the water. In general you do not need to be concerned about this scale as it only affects the maximum output amperage of the anode, not the anode’s required trickle output necessary to maintain effective corrosion protection. Zinc Carbonate is water insoluble, but can be readily removed by either alkalies or acids.

Howard

 

[abcandjrc]

But Baz's anodes are aluminum. That is what I was wondering about. My experience has always been with zinc, so what he was describing was foreign to me. I suspect what he is seeing is normal with aluminum, but I'd still look into it further to be sure.

Defender has this on its web site:
NEVER MIX Zinc and Aluminum Anodes on the same vessel.

Zinc Alloy Anodes = Salt water only
Not recommended for use in fresh water
Alloy is manufactured to meet or exceed US Military Specification (MIL-A-18001K)
Aluminum Alloy Anodes = Salt or Brackish water
Not recommended for use in fresh water
Proven to last longer than zinc due to increased capacity
Alloy is manufactured to meet or exceed US Military Specification (MIL-A-24779(SH))
Magnesium Alloy Anodes = Fresh water only
Not recommended for use in salt or brackish water
The only alloy proven to protect your boat in fresh water

Sounds like he should be OK from that as long as they don't disappear too quickly. They must be doing their job if they are oxidizing even if they do look like cauliflower.