Adding a zinc anode to a tin boat for saltwater use

[DaleH]

Zinc Anode Info: They say a picture is worth a 1,000 words, so I’ll be brief. Quite simply I don’t paint or I remove the paint where I’ll affix a common ‘rudder’ zinc to the hull.

For a zinc anode to work correctly, it must be in full contact with bare, clean metal. I drilled out, then wet out the wood transom core with thin epoxy, then imbedded a SS threaded-insert into the wood using thickened epoxy once the thin stuff had ‘kicked’ (tacky, i.e., starting to cure). This makes sure that the 2 epoxy layers chemically bond with each other, making a stronger junction, and albeit a waterproof one to boot!

Then I just affix the rudder zinc with a short SS bolt, gooped up well (bolt threads only) with marine synthetic water-resistant grease, e.g., OMC/Bombardier ‘Triple Guard’ grease.

Simple and it works 8) !

 

[Skiffing]

Easy to install - and a good thing to do.

This allumalloy anode was installed past spring. It is 3" X 6" x 0.5"

The boat was slipped for a couple of nights only and engine hours are about 100 since installation.

The pitting you see would have been aluminum corrosion.

 

[richg99]

Good job and a timely post for me. I am dragging my 1648 Lowe back to TX at the end of the week. Obviously, this boat has only been used in freshwater. I seem to remember reading that the zincs for saltwater are a different material than the zincs for freshwater.

Any input on this?

thanks, richg99

 

[DaleH]

Good job and a timely post for me. I am dragging my 1648 Lowe back to TX at the end of the week. Obviously, this boat has only been used in freshwater. I seem to remember reading that the zincs for saltwater are a different material than the zincs for freshwater.

Any input on this?

thanks, richg99

Yes, magnesium anodes are recommended for OBs in freshwater, as per www.boatzincz.com. See their Chart B for boats w/ no shore power connections, per https://www.boatzincs.com/index.html

Also reproduced below ....

 

[iam2sam]

Does the anode need to be below the water line for a boat that lives on a trailer?

SAM

 

[DaleH]

Does the anode need to be below the water line for a boat that lives on a trailer?

How's this Sam ... for a boat that lives on a trailer and is only in the water for hours to a few days ... you don't even need to install any anode IMHO =D> .

 

[Pappy]

Couple tips on zinc anodes.

If they look great after several months of usage? ....... they aren't working! Replace.
If they look like they get a coating of white scale on them?.......they aren't working. Clean and put back in use. Monitor.

Zincs, good zincs, will erode, pit, Look like Hell and "go away". That is what they are designed to do. If they aren't, they are not working.

 

[PSG-1]

As crazy as it may sound, the BEST anode for an aluminum boat is an aluminum anode.

It provides protection in salt, and brackish waters. Magnesium is too reactive for salt water, and will actually lift the paint off the boat. Zinc isn't reactive enough, and the boat will corrode if you leave it in the water for long periods of time.

 

[Jim]

Great thread! :beer:

I see an article coming on the homepage with all your expertise put into it.

Jim

 

[Crazyboat]

Does the anode need to be below the water line for a boat that lives on a trailer?

SAM

If you were going to install one, doing so above the waterline would serve no purpose.

 

[DaleH]

As crazy as it may sound, the BEST anode for an aluminum boat is an aluminum anode.

It provides protection in salt, and brackish waters. Magnesium is too reactive for salt water, and will actually lift the paint off the boat. Zinc isn't reactive enough, and the boat will corrode if you leave it in the water for long periods of time.

As @PSG-1 mentions, NOTE there are 3 different anode types available - zinc, aluminum, or magnesium. So choose the right one for your use. I used a 'zinc' as this boat was in saltwaters, but the other types may be a better choice for you.

A good source to buy these is www.boatzincs.com, as they sell all 3 materials in all sizes and shapes.

Zinc is the traditional anode choice for saltwater vessels.

Aluminum anodes are for use in all types of water: Salt, Brackish, and Fresh. They are an alternative to zinc anodes as they are 1) more active, 2) provide better self-cleaning performance, and 3) offer a longer service life. They are preferred for protecting vessels with marine grade aluminum underwater metals.

Magnesium anodes are the best choice for fresh water vessels (only).