Sea cocks

[Tranona]

Interesting as my Boat has from factory all of the seacocks bonded.. I shall consult with Nigel Calder again and see his take on seacock bonding..

I think you will find he agrees with me and that bonding (in the US) is primarily for lightening protection. It is a "fashion" for some builders, particularly of motor boats to bond all underwater metal fittings but there is no logical or scientific reason to do so. There are specific fittings that meet the conditions where a galvanic cell could form and an anode could be needed. The most common are yellow metal props and stainless shafts, mixed metal rudders, usually yellow metal and stainless, bow thrusters, aluminium and stainless, saildrives/outdrives, aluminium and stainless. In all cases these are mixed metals of different potential in contact in an electrolyte (seawater). A seacock does not have these properties, being a single metal in contact with GRP. One caveat, most ball valves do have mixed metals such as operating shafts of steel but they are not actually in contact in water, nor would an anode be of any use if they were because the anode has to be close to the item in line of sight. The latter condition is another reason why bonding to an anode would not be effective as most bonding circuits have anodes that are remote from seacocks. The photos show the hull anode protecting the stern gear on my boat. As you can see it is close to the propeller - recommendation is less than a metre and bonded to the shaft through a brush on the shaft inside. This is in addition to an anode on the prop which goes first because it is closer. None of the 5 seacocks have anodes and have been there since 1979.

 

[Boathook]

@Tranona nice 'fairing' leading the water to the prop.

 

[Fire99]

I think you will find he agrees with me

I would say he doesn't.
Here is Nigel and Jan talking on the topic. The conclusion is, if you have high quality Bronze thru-hulls then you don't need bonding to an anode. However, if you have inferior and common (these days) DZR thru-hull fittings then you DO need to bond them...
Interestingly Jan has gone down the route that I'm gradually doing down and replacing with Tru-Design plastic fittings..

Here is the short video on the topic. Well worth 4 minutes of people's time, since they state that boat builders speak of thru-hull fittings being replaced every 5 years on modern boats!!!!

 

[IanCC]

Interesting as my Boat has from factory all of the seacocks bonded.. I shall consult with Nigel Calder again and see his take on seacock bonding..

These days I treat "Calder" stuff with a lot of caution.

 

[Tranona]

I would say he doesn't.
Here is Nigel and Jan talking on the topic. The conclusion is, if you have high quality Bronze thru-hulls then you don't need bonding to an anode. However, if you have inferior and common (these days) DZR thru-hull fittings then you DO need to bond them...
Interestingly Jan has gone down the route that I'm gradually doing down and replacing with Tru-Design plastic fittings..

Here is the short video on the topic. Well worth 4 minutes of people's time, since they state that boat builders speak of thru-hull fittings being replaced every 5 years on modern boats!!!!

Well he is simply wrong. He does not understand the difference between DZR and plain brass which is understandable because DZR is not common in the US. It has been used for years here - Blakes have been DZR for over 40 years. There is no difference in corrosion resistance between DZR and the bronze alloy commonly used for seacocks and fittings. He is also wrong in that anodes will prevent dezincification in brass because the zinc is in the alloy rather than being a separate piece of metal.

The 5 years is also nonsense. The RCD simply says that material used in seacocks should have a MINIMUM life of 5 years. There are literally hundreds of thousands of seacocks in use in leisure boats, probably a majority made of plain brass. If you look around modern boats particularly sailing boats you will rarely find any form of bonding of seacocks because those builders understand the science of galvanic corrosion. It is simply not necessary. It is not unreasonable to say that seacocks should be regularly inspected, but not aware of any builder who specifically says they should be replaced every 5 years. However visual inspection is not very effective in identifying serious dezincification as you need to remove the seacock assembly and cut them open. There is rarely dezincification in the valves themselves, but almost always in the threads of the screwed fittings which are exposed to seawater. This can be largely avoided by doing what some builders now do and use plenty of sealant on the fittings.

There is a lot of misunderstanding and misinformation on this subject often spread by people such as surveyors who should know better.

Tru Design come from New Zealand and were developed because bronze and DZR were not readily available there. They are a viable alternative to metal but are not any different in corrosion resistance to bronze or DZR. Now they are more readily available and priced competitively in the UK it is not surprising that they have become popular, particularly given the misinformation about metals that has spread around over the last 10 years or so.

 

[Fire99]

These days I treat "Calder" stuff with a lot of caution.

Really?? I find his videos with Jan very informative and other than this thread, I've not heard any criticism on his electrical wisdom.

 

[Fire99]

Well he is simply wrong.

I take it you've watched the attached video and are basing your argument against what they are stating in the video?
The 5 year thing in the video is not how regularly they are suggested to be replaced. It is the directive on how long they have to last. Quite different..

Anyway, Calder has been well respected for a lot of years (I have one of his mechanical maintenance books from years ago) so if you are going to dispute what he says in this video, I'd appreciated some other sources of your opinion. Otherwise it's merely Tranona vs Calder.

Ps.. Why do you say Tru Design which are plastic are no more corrosion resistant than DZR? My understanding is these composite valves suffer none of the metal corrosion of DZR and will pretty much last decades.. They are certainly not cheaper than DZR. When fitted, mine were more expensive than the cheap DZR alternatives.

 

[IanCC]

Really?? I find his videos with Jan very informative and other than this thread, I've not heard any criticism on his electrical wisdom.

Not watched vids, but kniwledge has moved on from the book of his that i have. I don't refer to it anymore for anything other than background.

 

[Fire99]

Not watched vids, but kniwledge has moved on from the book of his that i have. I don't refer to it anymore for anything other than background.

Yes and no. Things like Tru-Design now exist that didn't in the past etc and our shift to Aluminium anodes etc but principles of physics haven't changed so old knowledge isn't obsolete.

The attached video isn't a history lesson. It's current, dealing with current (excuse the electrical pun) corrosion issues of currently available thru-hull fittings. And the conclusions of the video are in complete contrast with Tranona's views so it is the basis of the debate.

 

[Tranona]

Yes and no. Things like Tru-Design now exist that didn't in the past etc and our shift to Aluminium anodes etc but principles of physics haven't changed so old knowledge isn't obsolete.

The attached video isn't a history lesson. It's current, dealing with current (excuse the electrical pun) corrosion issues of currently available thru-hull fittings. And the conclusions of the video are in complete contrast with Tranona's views so it is the basis of the debate.

I take it you've watched the attached video and are basing your argument against what they are stating in the video?
The 5 year thing in the video is not how regularly they are suggested to be replaced. It is the directive on how long they have to last. Quite different..

Anyway, Calder has been well respected for a lot of years (I have one of his mechanical maintenance books from years ago) so if you are going to dispute what he says in this video, I'd appreciated some other sources of your opinion. Otherwise it's merely Tranona vs Calder.

Ps.. Why do you say Tru Design which are plastic are no more corrosion resistant than DZR? My understanding is these composite valves suffer none of the metal corrosion of DZR and will pretty much last decades.. They are certainly not cheaper than DZR. When fitted, mine were more expensive than the cheap DZR alternatives.

Yes I watched the video and he firmly belongs in the box of people who are spreading disinformation. Like many who should know better he does not understand the difference between DZR and plain brass. The alloy includes a small proportion of arsenic to prevent dezincification. See here for an explanation altecnic.co.uk/2021/09/01/dzr-brass-importance/ Calder has clearly not read that probably because the product is not widely used in the US. So it is not me against him it is truth against falsehood. You might also try coxeng.co.uk which is the website of Vyv Cox who apart from being a regular poster here is a well respected metallurgist who writes regularly on this subject in the yachting mags - often to correct false information peddled by others.

Calder and his mate are also wrong about the usage of plain brass seacocks in Europe. This long predates the RCD and most builders including high class ones like HR have been fitting them for decades. As I said the RCD simply set a minimum standard and there is plenty of evidence that plain brass lasts for many years - a lot longer than the minimum. If it were not the case we would have seen boats sinking frequently and regularly. Insurers would have banned their use years ago if they were indeed a cause of failure and sinking leading to claims.

The only thing they were right about was the description of dezincification in screwed fittings - just as I described. However as they pointed out the failure was in applying unusual force, not failing while doing the job of transmitting seawater into the boat. Also note that the mate said the units he replaced were sound when he cut them apart. Dezincification is more common in fittings for the reason I mentioned earlier plus the fact that while DZR valves have been freely available for years because they are standard domestic plumbing items. Through hulls, elbows and hose tails have been more limited and plain brass are often used instead of bronze or DZR. Just to reinforce the point, Blakes plug type valves have been made of DZR since the 1970s and there is no evidence they are affected by galvanic corrosion.

Just to confirm bonding to an anode will not prevent dezincification of brass fittings

Tru Design are no more corrosion resistant than DZR or bronze because none of the materials corrode in seawater.

Apologies for the length of reply but there is nothing here that I "made up" - all supported by science and evidence.

 

[Plum]

........ My understanding is these composite valves suffer none of the metal corrosion of DZR and will pretty much last decades..

Have you had DZR valves or fittings corrode? In my experience, they do not corrode. One of mine is now 25 years old and still good. (and it has never been bonded!)

 

[Fire99]

Have you had DZR valves or fittings corrode? In my experience, they do not corrode. One of mine is now 25 years old and still good. (and it has never been bonded!)

Yes I watched the video and he firmly belongs in the box of people who are spreading disinformation. Like many who should know better he does not understand the difference between DZR and plain brass. The alloy includes a small proportion of arsenic to prevent dezincification. See here for an explanation altecnic.co.uk/2021/09/01/dzr-brass-importance/ Calder has clearly not read that probably because the product is not widely used in the US. So it is not me against him it is truth against falsehood. You might also try coxeng.co.uk which is the website of Vyv Cox who apart from being a regular poster here is a well respected metallurgist who writes regularly on this subject in the yachting mags - often to correct false information peddled by others.

Calder and his mate are also wrong about the usage of plain brass seacocks in Europe. This long predates the RCD and most builders including high class ones like HR have been fitting them for decades. As I said the RCD simply set a minimum standard and there is plenty of evidence that plain brass lasts for many years - a lot longer than the minimum. If it were not the case we would have seen boats sinking frequently and regularly. Insurers would have banned their use years ago if they were indeed a cause of failure and sinking leading to claims.

The only thing they were right about was the description of dezincification in screwed fittings - just as I described. However as they pointed out the failure was in applying unusual force, not failing while doing the job of transmitting seawater into the boat. Also note that the mate said the units he replaced were sound when he cut them apart. Dezincification is more common in fittings for the reason I mentioned earlier plus the fact that while DZR valves have been freely available for years because they are standard domestic plumbing items. Through hulls, elbows and hose tails have been more limited and plain brass are often used instead of bronze or DZR. Just to reinforce the point, Blakes plug type valves have been made of DZR since the 1970s and there is no evidence they are affected by galvanic corrosion.

Just to confirm bonding to an anode will not prevent dezincification of brass fittings

Tru Design are no more corrosion resistant than DZR or bronze because none of the materials corrode in seawater.

Apologies for the length of reply but there is nothing here that I "made up" - all supported by science and evidence.

Interesting.. I see where you are coming from. I shall investigate further. Maybe your info should be passed on to Nigel Calder and see what his response is to this...

 

[Fire99]

Have you had DZR valves or fittings corrode? In my experience, they do not corrode. One of mine is now 25 years old and still good. (and it has never been bonded!)

All my previous boats had bronze valves. My current boat has every valve bonded and it in itself is over 20 years old and manufactured in the other side of the world. The only valve I have replaced (with Tru-Design) is due to the valve operation seizing so I'm not the best guinea-pig for this..

 

[Tranona]

Interesting.. I see where you are coming from. I shall investigate further. Maybe your info should be passed on to Nigel Calder and see what his response is to this...

No need for me to do anything. All the information I have provided is well known and in the public domain. For example Vyv has written more or less the same in both PBO and YM. If you google DZR you will find several sources giving the explanation as to why it does not corrode. The role of anodes in a galvanic circuit is well known and once you understand how it works you realise that it impossible for an external anode to prevent dezincification in common 60/40 brass.

Your boat is bonded because that is what the designers who commissioned the Taiwanese to make it asked for, not because there was any scientific need for it. Fortunately it does not normally result in any harm, but if some wally connects your bonding incorrectly to your boats electrics your seacocks will fizzle away and your boat will likely sink. That really happened to a forum member a few years ago and fortunately he noticed the smell and was berthed close to a crane which lifted the boat before too much water got in.

 

[Plum]

All my previous boats had bronze valves. My current boat has every valve bonded and it in itself is over 20 years old and manufactured in the other side of the world. The only valve I have replaced (with Tru-Design) is due to the valve operation seizing so I'm not the best guinea-pig for this..

That is good. You have been lucky. Buying skin fittings and seacocks simply labelled as "bronze" is a risk unless the supplier specifies the specific alloy used. For example both "Admiralty Bronze" and "Manganese Bronze" are not actually bronze at all, they are both brass, and will dezinc in seawater.

 

[PaulRainbow]

No need for me to do anything. All the information I have provided is well known and in the public domain. For example Vyv has written more or less the same in both PBO and YM. If you google DZR you will find several sources giving the explanation as to why it does not corrode. The role of anodes in a galvanic circuit is well known and once you understand how it works you realise that it impossible for an external anode to prevent dezincification in common 60/40 brass.

Your boat is bonded because that is what the designers who commissioned the Taiwanese to make it asked for, not because there was any scientific need for it. Fortunately it does not normally result in any harm, but if some wally connects your bonding incorrectly to your boats electrics your seacocks will fizzle away and your boat will likely sink. That really happened to a forum member a few years ago and fortunately he noticed the smell and was berthed close to a crane which lifted the boat before too much water got in.

I know someone with a not too old Hanse, with all of the below water skin fittings bonded. Not sure of the exact cause (not spoken with them recently), but for some reason the sail drive anode was totally depleted and the saildrive itself began to dissolve, along with all of the skin fittings.

Luckily the problem was found before any failed and the boat sank, but they did all have to be replaced.

 

[Fire99]

No need for me to do anything. All the information I have provided is well known and in the public domain. For example Vyv has written more or less the same in both PBO and YM. If you google DZR you will find several sources giving the explanation as to why it does not corrode. The role of anodes in a galvanic circuit is well known and once you understand how it works you realise that it impossible for an external anode to prevent dezincification in common 60/40 brass.

Your boat is bonded because that is what the designers who commissioned the Taiwanese to make it asked for, not because there was any scientific need for it. Fortunately it does not normally result in any harm, but if some wally connects your bonding incorrectly to your boats electrics your seacocks will fizzle away and your boat will likely sink. That really happened to a forum member a few years ago and fortunately he noticed the smell and was berthed close to a crane which lifted the boat before too much water got in.

It's not about 'need', it's in the best interests of boaters for there to be an agreed direction. Nigel Calder is extremely popular in the boating world so I think we owe it to other boaters to form agreed 'united fronts' on important issues..

Certainly an area I think I will look further into.

 

[Tranona]

It's not about 'need', it's in the best interests of boaters for there to be an agreed direction. Nigel Calder is extremely popular in the boating world so I think we owe it to other boaters to form agreed 'united fronts' on important issues..

Certainly an area I think I will look further into.

This subject has been rolling around for years and Calder is not the only one who misunderstands.

Its importance is also vastly overrated. Despite 60/40 brass being prone to dezincification it has been used for seacocks, mainly in Europe for decades and there has been no widespread epidemic of sinkings from failures. Even when fittings are dezincified and therefore lost strength they rarely fail when fulfilling their normal function because they are under no stress. Calder talks about hitting them, putting them in a fridge or throwing in a fire to "test" them, but this is not testing the properties they need to fulfil their function. I am unlikely to change his views - just let the science speak for itself.

Of course it is better to use the materials that have superior corrosion resistance as it eliminates a potential weakness. Consumers are much better informed now as a result of the increase in awareness and the wider choice of products. Old ideas take a long time to fall away and the practice of bonding seacocks to an anode in a circuit is well entrenched as it dates from the time when GRP boats came on the market filled with lots of electrics and studded with seacocks and other metal fittings. Galvanic action was not fully understood and bonding became the norm. As it normally does no harm there is little incentive to change - and indeed some builders used to promote it to differentiate their boats from "cheaper" ones.

 

[Fire99]

This subject has been rolling around for years and Calder is not the only one who misunderstands.

Its importance is also vastly overrated. Despite 60/40 brass being prone to dezincification it has been used for seacocks, mainly in Europe for decades and there has been no widespread epidemic of sinkings from failures. Even when fittings are dezincified and therefore lost strength they rarely fail when fulfilling their normal function because they are under no stress. Calder talks about hitting them, putting them in a fridge or throwing in a fire to "test" them, but this is not testing the properties they need to fulfil their function. I am unlikely to change his views - just let the science speak for itself.

Of course it is better to use the materials that have superior corrosion resistance as it eliminates a potential weakness. Consumers are much better informed now as a result of the increase in awareness and the wider choice of products. Old ideas take a long time to fall away and the practice of bonding seacocks to an anode in a circuit is well entrenched as it dates from the time when GRP boats came on the market filled with lots of electrics and studded with seacocks and other metal fittings. Galvanic action was not fully understood and bonding became the norm. As it normally does no harm there is little incentive to change - and indeed some builders used to promote it to differentiate their boats from "cheaper" ones.

Cheers, an interesting topic. When I get round to it I shall investigate.

 

[PaulRainbow]

What are Nigel Calders professional qualifications ? Engineer, electrician, or what ?

Isn't he primarily a journalist ?

He is clearly knowledgable, but that knowledge is not based on experience and he's known to be wrong on a number of subjects, bonding sea cocks is one of them.

See post #36