So do I de-bond my skin fittings

superheat6k

superheat6k

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Current thinking on bonding of underwater fittings is that generally they perform better left alone, rather than tying them all together to form otherwise unnecessary stray current paths through the otherwise isolated parts.

My new to me boat is 1991 vintage with what appear to be original fit seacocks (all ball valves) and associate skin fittings, which seem OK apart from a couple almost seized due to neglect, that will be replaced. No signs of pinking anywhere when examined from inside the boat.

All are tied together with heavy copper (6mm2) copper wire, which has parted from the fittings in a few places. This could be due to use of stainless jubilee clips to hold the bonding wires in position.

I haven't yet observed the state of the anodes, which are mounted just above the props, nor have I yet been able to check the integrity of the bonding circuit as whole (breaks noted), or prop to anode, which is the important link, in my view.

I have it on my 'out of the water' to do list to replace the zincs, their mounting bolts and the entire bonding system wiring, but I wonder if I would be better off disconnecting the bonds to the otherwise isolated skin fittings, and just keep the bonding linking between engine blocks, shafts, props and anodes.

Due to dirtiness of the seacocks identifying the material as DZR of just plain brass might not be too simple. I will clean off the muck layer and see if pinking is apparent anywhere once the boat is ashore.

Views please.
 
Have a look for any cast or stamped numbers. There will be PN25 or similar, which is the pressure designation, but there may also be a longer sequence of numbers / letters to identify the metal. CW602N or CZ132 is DZR brass, while CW617N or CZ122 identifies it as plain stamping brass (often nickel-plated).

Of course, don't forget the hose tails: these are probably more likely to fail than the valve. When you are ashore, get the hoses off the tails and inspect for any pinkness, both inside and out.
 
There seems to be a total contradiction on this topic between USA and UK. I researched this last year and as far as I can ascertain the main reason for recommending bonding in USA is lightning protection rather than corrosion protection. I unbonded my seacocks in about 1996 without any subsequent problems.
 
superheat6k said:
Current thinking on bonding of underwater fittings is that generally they perform better left alone, rather than tying them all together to form otherwise unnecessary stray current paths through the otherwise isolated parts.

My new to me boat is 1991 vintage with what appear to be original fit seacocks (all ball valves) and associate skin fittings, which seem OK apart from a couple almost seized due to neglect, that will be replaced. No signs of pinking anywhere when examined from inside the boat.

All are tied together with heavy copper (6mm2) copper wire, which has parted from the fittings in a few places. This could be due to use of stainless jubilee clips to hold the bonding wires in position.

I haven't yet observed the state of the anodes, which are mounted just above the props, nor have I yet been able to check the integrity of the bonding circuit as whole (breaks noted), or prop to anode, which is the important link, in my view.

I have it on my 'out of the water' to do list to replace the zincs, their mounting bolts and the entire bonding system wiring, but I wonder if I would be better off disconnecting the bonds to the otherwise isolated skin fittings, and just keep the bonding linking between engine blocks, shafts, props and anodes.

Due to dirtiness of the seacocks identifying the material as DZR of just plain brass might not be too simple. I will clean off the muck layer and see if pinking is apparent anywhere once the boat is ashore.

Views please.
Click to expand...

pvb said:
No need to bond skin fittings, indeed better left isolated.
Click to expand...

vyv_cox said:
There seems to be a total contradiction on this topic between USA and UK. I researched this last year and as far as I can ascertain the main reason for recommending bonding in USA is lightning protection rather than corrosion protection. I unbonded my seacocks in about 1996 without any subsequent problems.
Click to expand...

PetiteFleur said:
If you go to MG Duff website or the informative leaflet available at chandleries, it gives full details of anodes, bonding etc.
Click to expand...


I would definitely not bond any new DZR fittings, and remove the bonding from any others that can be identified as DZR

Unless there is any compelling reason to unbond any fittings which might be ordinary brass i would leave the bonding / cathodic protection in place until such time as they are replaced with DZR.

It is however important that the electrical wiring is kept in good order .... a point made by MG Duff

MGDuff used to be firmly in the bond everything camp but it appears that is no longer the case


Worth remembering that dodgy electrical wiring, bonded seacocks and the use of Tonval ( mistakenly believed to be dezincification resistant) were considered to be the contributing factors in the near loss of the FV Random Harvest some years ago
 
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I think about this every winter when the boat comes out of the water. The boat is 1978 built and all of the through hulls and the prop shaft are bonded to the pear anode. So far as I am aware this has always been the case. Many of the through hulls and some of the seacocks are original. I have never seen any hint of dezincification. So should I de-bond, because that is the latest thinking, or leave well alone, because it's lasted 37 years so far. Up until now I have chosen the latter and I suspect I will continue thinking that.
 
vyv_cox said:
There seems to be a total contradiction on this topic between USA and UK. I researched this last year and as far as I can ascertain the main reason for recommending bonding in USA is lightning protection rather than corrosion protection. I unbonded my seacocks in about 1996 without any subsequent problems.
Click to expand...

You are correct. All my skin fittings are bonded to a sintered bronze plate bolted to the keel. All my skin fittings and seacocks are bronze and are in perfect condition after 31 seasons use.
 
alahol2 said:
I think about this every winter when the boat comes out of the water. The boat is 1978 built and all of the through hulls and the prop shaft are bonded to the pear anode. So far as I am aware this has always been the case. Many of the through hulls and some of the seacocks are original. I have never seen any hint of dezincification. So should I de-bond, because that is the latest thinking, or leave well alone, because it's lasted 37 years so far. Up until now I have chosen the latter and I suspect I will continue thinking that.
Click to expand...

My boat was built in '73 and commissioned in 74, everything was bonded to the anode. Over the years it is obvious that bonding has broken and been repaired while the wiring flex had become brittle and failed in places. I removed the bonding from the seacocks and pulled all the wiring back in 2009. No issues at all since them but I doubt that the bonding was even complete before I bought the boat. I would agree though that if your is in good condition and you have no issues, then why would you want to change it. I am not sure if this is relevant but my own boat was fitted with SSB, removed before I purchased her. She has copper strapping running around the hull that is part of the bonding circuit and iirc attached to the sintered block on the hull. I think it was something to do with the SSB set up, so SSB may have been the reason as opposed to protecting the seacocks, which are all Blakes. The point is all the underwater stuff that I can see is in good condition, except the anode of course, from a yacht that was bonded but is not now.
 
Orion Jim said:
You are correct. All my skin fittings are bonded to a sintered bronze plate bolted to the keel. All my skin fittings and seacocks are bronze and are in perfect condition after 31 seasons use.
Click to expand...

Bronze seacocks and fittings certainly seem more widely available in the US, which would seem to support Vyv's suspicion about lightning protection, since any true bronze really doesn't need galvanic protection.
Over here many new boats leave the factory with plain brass underwater fittings, unbonded.
 
Ruffles said:
Presumably connecting a bronze sea cock to a less noble brass one will actually accelerate the erosion of the brass!
Mine were bonded with bare cable ends attached with jubilee clips. Unlikely to be much use....
Click to expand...

Yes, that is a likely outcome, although fortunately all the copper alloys are fairly close in the galvanic series. The jubilee clip connector appears quite regularly and is pretty much useless. The voltages involved are very small and are easily blocked by bad connections. Better not to bother, although if a 40 year old boat has survived bonding with no seacock corrosion I can think of more worthwhile activities than stripping it all out.
 
I've always left seacocks unbonded.

The US recommendations are shown in:
ABYC E-01 Bonding
ABYC E-04 Lightning
You can Google them if interested.
Basically they say it isn't compulsory to bond seacocks.
 
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