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rbrasi 01-04-2013 01:23 PM

Bonding
 
In regards to bonding to prevent galvanic corrosion:
If I am bonding thru hulls (marine bronze), what is the best material to use to adhere the Copper wire to the seacock? Is there such a thing as bronze tape?

I have read older threads and can't seem to find a definitive answer. I do understand that it is somewhat of an antiquated notion. I already have zinc anodes protecting the other metals in the water.

Brewgyver 01-04-2013 02:00 PM

Re: Bonding
 
For galvanic protection only, just use copper straps made for the purpose. They come with a screw lug to attach the wire. If you don't have a local electrical supply house, you can order them from McMaster-Carr (link to specific product).

mitiempo 01-05-2013 04:13 AM

Re: Bonding
 
If your through hulls are manganese bronze I would be surprised. All good quality bronze through hulls I know of (Groco, Apollo/Conbraco) are 85-5-5-5 bronze which has 5% zinc. I believe it needs to be 10% zinc to have dezincification issues. There is, in my opinion, no advantage to bonding through hulls. Stan Honey gives reasons here: Grounding
Bonding a through hull that is isolated and all of one metal in composition is only inviting it to have issues.

Your prop is probably manganese bronze which contains up to 39% zinc and does need galvanic protection.

Barrosa 01-05-2013 06:23 AM

Re: Bonding
 
Could anyone tell what the stuff is this bonding??? I am totally new here and dont know the meaning of it.. Any adivce would be apppreciated.......

boatpoker 01-05-2013 08:46 AM

Re: Bonding
 
Quote:

Originally Posted by Barrosa (Post 971165)
Could anyone tell what the stuff is this bonding??? I am totally new here and dont know the meaning of it.. Any adivce would be apppreciated.......

Very complex and controvertial subject.... All metals have a natural voltage potential (this part is not controvertial). The idea of bonding is that if you connect all underwater metals it will equalize those voltage potentials therefore no galvanic current will flow, thereby eliminating glavanic corrosion.

I have my own ideas about whether its a good or bad thing to do but I don't want to start a flame war :)

misfits 01-05-2013 09:33 AM

Re: Bonding
 
Quote:

Originally Posted by mitiempo (Post 971153)
Bonding a through hull that is isolated and all of one metal in composition is only inviting it to have issues.

What a subject :confused:

What do you consider "isolated"? Does a rubber hose that connects a thru hull isolate it? If so what's the advantage of bonding or not bonding?

There's so many different opinions on this subject. A surveyor that I know & respect said in Europe it's common practice not to bond any thru hulls because they feel they're "isolated" when connected with a rubber hose. However when there's seawater sloshing around in the bilge the opportunity presents itself to "connect" all underwater thru hulls to the keel which is lead & the disimilar metal issue comes into play.

He also said he's for bonding providing all electrical connections are without corrosion so there's no resistence so everything is equal.

Personally I'm so confused about this subject I'm wondering if there is a right or wrong answer.

boatpoker 01-05-2013 09:52 AM

Re: Bonding
 
Told ya !

If you are really interested in this and any other electric issues I highly recommend you visit Captain David Rifkin's website and look under "Documents". His website is a goldmine of clear and concise articles on marine electrical issues.

Dave is a retired nuclear sub commander, corrosion consultant to USCG and USN and one of the top guys in this field. I took one of his seminars a few weeks back and was greatly impressed.

Maine Sail 01-05-2013 10:39 AM

Re: Bonding
 
Quote:

Originally Posted by boatpoker (Post 971211)
Told ya !

If you are really interested in this and any other electric issues I highly recommend you visit Captain David Rifkin's website and look under "Documents". His website is a goldmine of clear and concise articles on marine electrical issues.

Dave is a retired nuclear sub commander, corrosion consultant to USCG and USN and one of the top guys in this field. I took one of his seminars a few weeks back and was greatly impressed.

I too have taken courses with David Rifkin and he is excellent. Everett Collier is also excellent.

The problem with this issue is that EVERY BOAT IS DIFFERENT!!!!!!!!!

Articles like the Stan Honey/WM Advisor article do a big disservice to the boating community, IMHO. That article over simplifies and leaves out a lot of pertinent information. I have actually had this very pointed conversation with Stan and he agreed that his article is very often interpreted incorrectly and people read what they want to read.

When it comes to things like lightning bonding, AC/DC Earth bond on-board, underwater metals bonding etc. etc. people tend to take only what they want to hear from an article without fully understanding the basis for any of the bond or not to bond arguments.

Our own vessels remains with the seacocks un-bonded, but, I have a bone dry bilge and our boat is impeccably wired compared to 99.5% of the boats out there.

Un-bonding the underwater metals on some vessels can cause major issues yet some boats can be un-bonded and not suffer issues or actually do better. This is why even the "experts" disagree on the topic of bonding. The only real truth is that YOUR BOAT should, at a bare minimum, undergo a full corrosion survey before making any of these changes.

Reading a "one pager" in the WM catalog does not even begin to scratch the surface of giving you even a baseline for understanding marine corrosion. I have yet to see a marina full of boats where a blanket "one size fits all" approach could be applied without in-depth analysis of each vessels electrical systems..

How many boat owners have, understand or use a Ag/AgCl reference cell? Hell, we can't even get people to install zincs correctly yet the WM Advisor is telling you to "unbond"....? Great.... Go for it......;) :eek:

Without a full corrosion survey I would strongly advise people not heed the overly simplistic advise of the WM article until you have a full grasp of what Stan was actually saying! Unless you have a full understanding of marine corrosion and have done a very, very thorough corrosion survey on your own vessel hold off on any changes until you have a better analysis of your vessel.... You may be very surprised at what you find....;) You'd be horrified at what I find.....

rbrasi 01-05-2013 12:42 PM

Re: Bonding
 
Here is my rationale:
When I bought my boat, the thru hulls were bonded by the original owner. He owned the boat nearly 40 years and did everything right. It's become my rule of thumb on this ongoing project to just copy what the old guy did and I'll be fine. So, last year, a different guy who brokered the sale to me told me that bonding will not be necessary once we replaced the thru hulls (Groco). I went with that, and now 18 months later, I see that there is some green on a couple of the thru hulls. This tells me there is corrosion, so I bonded them yesterday. I will watch closely to see if anything changes. The question is, if they are correctly protected, then how long would it be before I begin to see the signs of corrosion? Also, since I am basically getting the boat ready for the next owner, I have to think in terms of what the surveyor will report. Maybe I should run this by a local who knows (Los Angeles).

Maine Sail 01-05-2013 01:11 PM

Re: Bonding
 
Quote:

Originally Posted by rbrasi (Post 971277)
Here is my rationale:
When I bought my boat, the thru hulls were bonded by the original owner. He owned the boat nearly 40 years and did everything right. It's become my rule of thumb on this ongoing project to just copy what the old guy did and I'll be fine. So, last year, a different guy who brokered the sale to me told me that bonding will not be necessary once we replaced the thru hulls (Groco). I went with that, and now 18 months later, I see that there is some green on a couple of the thru hulls. This tells me there is corrosion, so I bonded them yesterday. I will watch closely to see if anything changes. The question is, if they are correctly protected, then how long would it be before I begin to see the signs of corrosion? Also, since I am basically getting the boat ready for the next owner, I have to think in terms of what the surveyor will report. Maybe I should run this by a local who knows (Los Angeles).

Green is not necessarily corrosion at all. It is "verdigris" the green patina all bronze, copper and brasses can undergo when exposed to wet salty environments. The statue of liberty is a prime example of verdegris...

If your seacocks start to turn "pink" they you need to start worrying.. If you mixed yellow brass or any dissimilar metals in your seacock system then you can begin to worry. The most often "mixed" metal in a seacok system is when people try to cut corners on the male adapters and use Home Depot quality 60/40 yellow brass.
http://www.pbase.com/mainecruising/image/108638190.jpg


The thru-hull, seacock or ball valve body AND the male adapter or ANY nipples or elbows should all be of 85-5-5-5 bronze.

The green, in and of itself, is not a concern and is normal. It is what may be under the green that would be cause for concern. Green is ok but green can hide real corrosion so green can be bad if the seacocks are not cleaned and examined every now and then. Heck look at the bronze portlights of any older Cape Dory they are green with verdigris but are not submerged in an electrolyte.... If you want to minimize verdigris it slather a clean seacock with Lanocoat...

This is a good example of why articles like the WM Advisor/Honey article are so dangerous. We don't even understand the difference between a natural patina of bronze in a marine environment and what real corrosion looks like.

Below is a picture of dealloying or dezincification of brass. This is real corrosion and quite dangerous. Note the pink color to what used to be a goldish yellow piece of brass. This is why brass should not be used below waterline for seacocks, bonded or not. The "green" on this valve had nothing to do with this corrosion. The "zinc" content in the brass, upwards of 40%, clearly became the sacrificial metal to the 85-5-5-5 bronze thru-hull fitting or other more noble metals.

These were not bonded and if they were they would have likely survived better, in this particular application. Again, no one size fits all... When the wrench was put to this valve it literally crumbled because there was no zinc left in it. Proper 85-5-5-5 bronze seacocks are VERY, VERY, VERY resistant to dezincification. I have many customers with 40+ year old tapered cone 85-5-5-5 bronze seacocks in as good a condition, corrosion wise, as when they left the factory
http://www.pbase.com/mainecruising/image/140701822.jpg


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