Aluminum Anodes and Bronze Propellor - Antifouling

Hi TF,

I recently replaced all my anodes with aluminum ones due to the SideShift thrusters only offering aluminum options. Since it's generally advised not to mix different types of anode metals, I'm unsure about which anti-fouling paint to use for my propeller. I've only come across zinc-based options so far. Any recommendations?

I'm not an expert, but I thought aluminum anodes were for boats that are stored in fresh water. Are you in fresh, or salt water? on my last boat I had a side shift thruster, and I always put zinc anodes on it.

Aluminum anodes are good in any water. Zinc anodes are only good in salt water. Magnesium anodes are only good in freshwater. Aluminum anodes are better for the environment than zinc anodes.

Thank you for your reply @Snapdragon III. Just to clarify, aluminum anodes are suitable for both brackish and saltwater environments. Currently, SideShift only provides aluminum anodes for their thrusters. I'm still hoping to receive some helpful advice regarding my original question about anti-fouling paint for my propeller.

Actually aluminum are good for any waters not just brackish or saltwater. Sorry I don’t paint my props so I can’t make any recommendations on that.

Learn something new every day. Now that I think of it, the last time I dug deeply into anodes was when I was dealing with corrosion issues on my old Aluminum boat. Obviously Aluminum anodes would not have been appropriate for an aluminum boat, so it makes sense that my memory would be that they are a poor choice.

I would imagine Prop Speed would be good for your propeller. I've never used it, but I think it is a silicone product, not zinc.

Snapdragon III said:

Obviously Aluminum anodes would not have been appropriate for an aluminum boat,

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Aluminum anodes are fine for protecting aluminum. All anodes are alloys, and the aluminum ones are still less noble than the aluminum used to build boats and for marine equipment.

I agree prop speed is the best thing to coat your prop with. It not only keeps the marine growth from fouling your running gear, it also helps minimize galvanic corrosion because it seals the metal from the electrolytic solution. I generally see much less wasting of anodes on running gear that has been coated with PS.

Comodave said:

Actually aluminum are good for any waters not just brackish or saltwater. Sorry I don’t paint my props so I can’t make any recommendations on that.

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Fleming said:

Aluminum anodes are fine for protecting aluminum. All anodes are alloys, and the aluminum ones are still less noble than the aluminum used to build boats and for marine equipment.

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I had the same questions when I found Sidepower only offered Alum anodes.

Above are correct as far my research revealed.
Alum anodes are an alloy that still works. I also learned that thrusters are not bonded so are a separate cell from other metals aboard. While the engine is connected to other metals via ground/bonding the water that pencil anodes reside in is far distant from hull & running gear that it a separate cell.

My understanding is that the caution against mixing anode materials applies to hull & running gear and NOT to engine or thruster anodes.

I have used Performance Metal pencil anodes and they advertise "THE ONLY ANODE THAT WORKS IN ALL TYPES OF WATER"

https://performancemetals.com/

I also don't paint prop so can't offer any info there

I use Rustoleum cold galvanizing spray paint on my props and it works great. I think it would be ideal with aluminum alloy anodes because it's just slightly less noble and therefore would erode/ablate/dissolve first, which would remove growth on the props.

ahoy said:

Hi TF,

I recently replaced all my anodes with aluminum ones due to the SideShift thrusters only offering aluminum options. Since it's generally advised not to mix different types of anode metals, I'm unsure about which anti-fouling paint to use for my propeller. I've only come across zinc-based options so far. Any recommendations?

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I believe if you look carefully at your Side Power installation instructions you will find that Side Power recommends isolating the thrusters from the boat's bonding system, relying only on the thuster's dedicated (aluminum) anodes. Doing so makes the aluminum anodes "standalone", meaning they are not electrically connected to your other anodes, regardless of their composition. That way, the aluminum anodes will not protect your less noble zinc anodes and in this case, is an acceptable practice.