Zinc basics 101

[njlarry]

After a search of all zinc topic posts I am still confused the proper way to find stray currents and determine the proper amount of zinc. My boat was one month in salt water and two months in brackish water in a marina next to new power boat that ran the AC constantly.
When hauled the shaft zinc was gone, but the shine on the shaft made me think it had only recently come off. The new pencil zinc in the heat exchanger was also completely gone.
So I assume there must be a stray current problem. How do I find it?
BTW, all the bronze thru hulls are bonded to the engine or the neg bus bar as is the fuel tank and fill.
Thank you for any info.

 

[Don S/V ILLusion]

The proper way is to use a silver chloride anode voltage monitor.

You may have a self-inflicted problem. By your description, I infer you have multiple grounds meaning multiple potential differences. Having a neighbor boat on constant power means nothing unless you have a boat susceptible to electrolysis.

 

[RichH]

Here ya go - reference anode: http://www.boatzincs.com/corrosion-reference-electrode.html

Your find the problem by switching off 'stuff' until the reference probe readout goes back to 'normal'.
Most such problems are usually wiring faults in a marina or from other boats .... be SURE to use a galvanic isolator on the GROUND wire coming into your boat's AC line. Without an isolator youre tied in electrically to every other boat in a marina through the common ground wire on the AC circuitry.

 

[njlarry]

Thank you both.
Not sure if I have an isolater but will add one for sure. Will let Santa know about the silver chloride anode.
From what I read it also looks like I should unground the thru hulls so that they isolated from galvanic charges.

 

[RichH]

From what I read it also looks like I should unground the thru hulls so that they isolated from galvanic charges.

.... at the risk of serious lightning damage if the boat is ever struck.
If the zinc. etc. anode is also electrically connected through a separate 'bonding' system that also connects to the through-hulls and other underwater metal, then those through hulls, etc. are also protected. The primary purpose of the bonding system is for lightning protection especially for 'side flashes' between metal components on the boat; plus, the intent of the bonding system is to provide multiple points from which lightning can exit (more safely) from the boat ... instead of going 'through' the fiberglass hull.

 

[McIntoshUSA]

Any recomendation on brands to get or not get for the silver chloride anode voltage monitor?

Thanks

 

[RichH]

Since you live in the lightning capital of the world ... contact and ask a local marine electrician. Your boatyard will probably know which ones to contact.