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-   -   zincs for lead. (http://www.sailnet.com/forums/gear-maintenance/23723-zincs-lead.html)

feetup 10-04-2006 07:25 PM

zincs for lead.
 
Do I need to have dedicated zincs on a lead keel, or is it sufficient to ground the keel bolts to my main anti galvanic ground? The only metal in the water is the keel and the rudder post.( and the outboard when I use it) I have no metal through hull fittings.

Feetup.

Sometimes it just doesn't get any better.

capn_dave 10-04-2006 08:17 PM

Ahoy Feetup, Iam not sure what you mean by
 
the main anti galvanic ground term.

A zinc is used to stop galvanic action between dissimlar metals. Like the prop (bronze) and a stainless shaft. They are also used on outboards and for protection of the aluminum and stainless parts .

Don't get bonding and grounding confused, they are two seperate issues. If you could please expound on the term you used.



Fair Winds

Cap'n Dave

Fstbttms 10-05-2006 12:57 AM

Quote:

Originally Posted by feetup
Do I need to have dedicated zincs on a lead keel...?

No. Lead is low enough on the periodic table that anodic protection is generally not needed.

feetup 10-05-2006 12:37 PM

To Captn Dave
 
I'm sorry, my semantics are wandering. I used the term ground but as you pointed out (thank you) I did in fact mean bonding. The question would be then, is it neccessary to have a zinc directly on the lead keel, or to run a BONDING wire from the keel bolts (stainless) to a dedicated bonding loop when the only submersed metals are the keel, the rudder shaft and sometimes the outboard. The boat is 1983 and showing no signs of galvanic corrosion even though I can't find a zinc anywhere. There may have been one, but I bought it on the hard and I cant see anything.

Rockter 10-05-2006 08:45 PM

Stainless and lead with a zinc connected to all of them?

Zinc is more reactive then iron, and iron more than lead. I think the zinc would help both.

I understand that lead is quite stable in salt water, and more so in fresh water.

Be wary at the interface between the stainless and the lead. It is likely to get oxygen depleted. Do your best to keep chlorides (borne by salt water) out of there. It will not be easy perhaps, but stainless is very unforgiving in oxygen-depleted, salty conditions. It really must be oxygenated in chloride-rich conditions, or is reacts quickly with the chlorine.

I would be more trusting of carbon steel keel bolts in those conditions. It is a more predictable material when oxygen gets depleted.

sailingdog 10-06-2006 12:30 AM

I wouldn't trust carbon steel keel bolts unless they were galvanized.

capn_dave 10-06-2006 07:21 AM

Ahoy Feetup
 
You don't need a zinc for the keel. Yep Dog right on no carbon steel bolts fer me either.

Fair Winds ya all. bringing a boat to Fl, on the delevery from hell

Cap'n Dave

Rockter 10-06-2006 08:54 AM

Be wary of that stuff they call stainless.

If you hide it, or shield it, and get salt water in there, and it gets oxygen depleted, be ready for surprises, all of them unpleasant.

It adores topsides with all that oxygen-laden seawater splash where the chlorine cannot get a bite at it, but a keel bolt is very often not so blessed.

Dry, certainly, but not salt-water wet, with salt water leaking into the threads, and stagnating.

capn_dave 10-06-2006 11:56 AM

Rockter there are
 
many grades of stainless. They use it fro prop shafts. The stainless for keel bolts is not the same grade as for topsides.

Do a little research before you make blank statements. Chekc out monel, a from os stainless< also check out 304, 316 on and on. All have a specific use.

Fair Winds

Cap'n Dave

Rockter 10-06-2006 01:19 PM

Blank, is it?

On my own propshaft, a little trace of corrosion dripped from the stuffing box on to the shaft. I ignored it, for like, two weeks. Man, it's got a hole in it now.

Yes, it's called stainless, and yes it's sold for propshafts, and yes it corrodes like crazy if you starve it of oxygen.

What is the correct grade for keel bolt?

I hope for his sake it's not the same stuff used for my shiny propshaft, a material provided by a big machine shop in a big fishing port.... I mean, they ought to know, shouldn't they?

Just about anything above 12% chrome is sold as stainless, including dinnerware. I look forward to you recommending a stainless grade for keel bolts, in chloride rich, oxygen-depleted environment.

I am all ears.

He could learn it the way I did, all over again, but it is a keel, after all, and not a propshaft.


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