Refurbishing a Zinc Anode

[fstbttms]

Originally Posted by savoir

It would only benefit if the other end of the wire was attached to the engine block or gearbox.

And even then the benefit is questionable, as the amount of protection provided by an anode is reduced by the increased resistance created by a long connection run and the inherent multiple connections.

[Jim Cate]

Originally Posted by boatpoker

some say it lasts longer, I'm not so sure ... too many variables.

Honest question: How much corrosion protection is needed in fresh water? Seems a different set of issues than salt water.

Jim

[Nightsky]

As long as you felt there was enough anode left to last another year or til your next haul-out, all that is necessary is to pressure wash them clean, usually done when the boat is hauled out, or by a diver, using a stainless steel wire brush only. I would not grind them at all.

[newhaul]

Originally Posted by fstbttms

And even then the benefit is questionable, as the amount of protection provided by an anode is reduced by the increased resistance created by a long connection run and the inherent multiple connections.

Well my hanging zinc is getting eaten and my prop zinc is lasting a lot longer now than it was before I added the hanging one. ( I use old big boat hull plate zinc's larger surface area). Free from most boat yards in my area.

[Kenomac]

Originally Posted by Nightsky

As long as you felt there was enough anode left to last another year or til your next haul-out, all that is necessary is to pressure wash them clean, usually done when the boat is hauled out, or by a diver, using a stainless steel wire brush only. I would not grind them at all.

I didn't haul the boat out. The one on the hull is fine, brushed it off myself just the other day. The refurbished anode is the prior anode I found laying around in a compartment.

[boatpoker]

Originally Posted by Jim Cate

Honest question: How much corrosion protection is needed in fresh water? Seems a different set of issues than salt water.

Jim

Galvanic corrosion in fresh water is significantly lower than in salt water but it does occur if the stars and stupidity align i.e. letting bottom paint contact i/o assemblies or worse painting those assemblies with anti-fouling or using zinc anodes which will last forever.

Fresh water varies considerably from harbour to harbour as some pollutants in the right density may be even more conductive than salt water.

[sailingharry]

Two comments:

1:. Use aluminum, not zinc. Zinc forms an innerting crust, and causes some environmental concern. Al does not form a crust, and works better. Yes, we've used zinc forever -- we were wrong.
2:. A external anode (guppy) will provide additional protection and extend the life of your prop anode. Just make sure it is connected to the ground system. On sailboats, a shroud usually works for this.

[newhaul]

Originally Posted by sailingharry

Two comments:

1:. Use aluminum, not zinc. Zinc forms an innerting crust, and causes some environmental concern. Al does not form a crust, and works better. Yes, we've used zinc forever -- we were wrong.
2:. A external anode (guppy) will provide additional protection and extend the life of your prop anode. Just make sure it is connected to the ground system. On sailboats, a shroud usually works for this.

A shroud only works if the chain plate is connected to the vessels bonding strap system personally I would recommend running the "guppy" to the bonding system not just clipped to a shroud.

[jhulmer]

Originally Posted by Dan_K

The chemical composition of the zinc anode is critically important. Iron needs to be limited to 0.025 weight percent of the anode. With a high iron content the zinc will form a crust and cease to be a sacrificial anode. I did a failure analysis of a very large steel ship that suffered millions of dollars damage due to pitting of the hull. To "save" money they bought anodes made in someone's basement that contained much higher iron than the specification allowed. All the zincs formed this crust and allowed the pitting to occur. Please be very careful with your zincs.

I attended a seminar at the Annapolis boat show conducted by Bob Campbell.
He was very specific about cheap alloyed zincs available these days. He said they reach a corrosion level that insulates them from contact with the water and then you have little to know protection.

He said only use Mil Spec zincs that are pure. you can tell they are Mil Spec because they have it stamped into the zinc.

[savoir]

No one should connect any zinc grounding wires to a shroud regardless of how good the bonding system below might be. Stainless steel is not a good conductor.

[sailingharry]

OK, I'll bite. On my boat, my shrouds are tied into the grounding system. I'm pretty sure it's an ABYC requirement, but I could be wrong. I know it was stock configuration on my '79 Sabre. But perhaps on other boats it's not done that way. On my boat, the portion of the stainless that is in the circuit is about 8" (the chainplate down to the grounding wire), and fairly trivial resistance. I built my own "guppy" so my wire is copper and my alligator clip is solid copper, unlike commercial ones that use a stainless cable and a copper coated steel alligator clip, so I'm probably ahead of commercial varieties.

So, for those that don't use the shroud, how do you run it? On my boat, that would be down the companionway to the engine block is probably the closest run. Messy, but it does avoid the stainless chainplate.

[sailingharry]

Oh -- the big reason I built my own guppy is that, as far as I can tell, no one sells an aluminum guppy yet. Besides, it's cheaper that way. Buy a nice big aluminum "divers delight," bolt it to a length of #10 copper with a copper alligator clip on the end. And when the guppy wastes away (about 2-3 years), you only need to replace the anode.

[newhaul]

Originally Posted by sailingharry

OK, I'll bite. On my boat, my shrouds are tied into the grounding system. I'm pretty sure it's an ABYC requirement, but I could be wrong. I know it was stock configuration on my '79 Sabre. But perhaps on other boats it's not done that way. On my boat, the portion of the stainless that is in the circuit is about 8" (the chainplate down to the grounding wire), and fairly trivial resistance. I built my own "guppy" so my wire is copper and my alligator clip is solid copper, unlike commercial ones that use a stainless cable and a copper coated steel alligator clip, so I'm probably ahead of commercial varieties.

So, for those that don't use the shroud, how do you run it? On my boat, that would be down the companionway to the engine block is probably the closest run. Messy, but it does avoid the stainless chainplate.

I run the cable thru the Dorado vent for the engine room. To the engine block.
Also ABYC standards are recommendations not regulations.
That being said the ABYC have done lots of testing and collection of data to come up with these standards and recommendations. ( means they are a good thing ) .

[boatpoker]

ABYC Standards do set a standard for bonding requirements from the standing rigging for lightning protection only. No reference is made to galvanic corrosion in this standard. The standards say absolutely nothing about "guppy's".

Guppy's may or may not help depending on placement, conductors and as fastbottoms said ... resistance.

[boatpoker]

Originally Posted by newhaul

I run the cable thru the Dorado vent for the engine room. To the engine block.

"Dorade"