Anodes and Air Conditioning

[thinwater]

Most boats have anodes due to dissimilar under water metals in the drive line, or just to protect what is there. However, I have zero immersed metals when my twin outboards are retracted. No anodes, except on the motors.

Now I have installed AC. The through hulls and most of the piping is plastic, but the strainer and AC unit contains some metal parts. The factory (yes I called engineering) says follow ABYC, but I can't see where any of that referrers to this case (no submerged metals, only strainer and AC).

Thoughts? Mounting and external zinc seems awkward. If the only contact is bronze in the strainer and copper in the AC, does it matter?

[thinwater]

No one? I could easily add an anode at a tee if needed. Is this ever done for plumbing? I know there are similar systems some times installed to reduce plumbing biofouling.

http://www.dtic.mil/dtic/tr/fulltext/u2/a557490.pdf

Clearly, unprotected copper pipe fouls less, but at the cost of corrosion:


And even the anode types makes a difference:

[poiu]

Originally Posted by thinwater

Most boats have anodes due to dissimilar under water metals in the drive line, or just to protect what is there. However, I have zero immersed metals when my twin outboards are retracted. No anodes, except on the motors.

Now I have installed AC. The through hulls and most of the piping is plastic, but the strainer and AC unit contains some metal parts. The factory (yes I called engineering) says follow ABYC, but I can't see where any of that referrers to this case (no submerged metals, only strainer and AC).

Thoughts? Mounting and external zinc seems awkward. If the only contact is bronze in the strainer and copper in the AC, does it matter?

An interesting question. Maybe if you look carefully the coil may be isolated. Have you measured resistance to ground? What's its alloy? Maybe something special?

[a64pilot]

If you add say a pencil anode, it of course has to be connected electrically to the coil.


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[thinwater]

Originally Posted by a64pilot

If you add say a pencil anode, it of course has to be connected electrically to the coil.


Sent from my iPad Pro using Cruisers Sailing Forum

Obviously. The strainer is bonded. I question if it is needed, if the only metals are bronze and copper, and honestly, it is only the copper I am concerned about.

One option, I guess, is to watch the bronze for evidence of de-zinc.

[sailorchic34]

Generally you'll have rubber or plastic tubing between the strainer and the copper coil. As such there is no current path to cause galvanic corrosion. For galvanic corrosion to occur both metals would need to be in physical contact with each other. No contact, no galvanic corrosion.

Anodes are not needed, generally for AC.

Bronze and copper are practically the same in the galvanic series, so no real galvanic action. Yellow brass on the other hand would dezinc.

[thinwater]

Originally Posted by sailorchic34

Generally you'll have rubber or plastic tubing between the strainer and the copper coil. As such there is no current path to cause galvanic corrosion. For galvanic corrosion to occur both metals would need to be in physical contact with each other. No contact, no galvanic corrosion.

Anodes are not needed, generally for AC.

Bronze and copper are practically the same in the galvanic series, so no real galvanic action. Yellow brass on the other hand would dezinc.

One concern is stray current. The boat has a galvanic isolation, so in principle it is NOT connected through the shore power to other boats, only to a copper ground plate.