Brass skin fittings failures

[fergie_mac66]

A lot of people (also socalled experts) say that the dezincification can be avoided by connecting the seacocks to an anode!
This however is bull**** sorry bull excrements !
The problem is that the zinc "anode" is already within the brass seacock and is eaten away!

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Also discussed in the MAIB report. Bonding of seacocks was a contributory factor in the near-sinking.

Only Just read this thread and know very little about this subject I wonder whether bonding the seacocks to magnesium anodes(changing from ordinary zinc ) would make any difference On boat that already have their seacocks bonded ?

What prompts me to ask this is a an issue with an outboard in freshwater where I was advised to switch to a magnesium anode

 

[Tranona]

Only Just read this thread and know very little about this subject I wonder whether bonding the seacocks to magnesium anodes(changing from ordinary zinc ) would make any difference On boat that already have their seacocks bonded ?

What prompts me to ask this is a an issue with an outboard in freshwater where I was advised to switch to a magnesium anode

Unless the seacocks are electrically connected to something else there is normally no need to bond them to an anode - zinc or magnesium. Anodes are only necessary when there are two bits of dissimilar metal in electrical contact, typically props and shafts.

 

[VicS]

Only Just read this thread and know very little about this subject I wonder whether bonding the seacocks to magnesium anodes(changing from ordinary zinc ) would make any difference On boat that already have their seacocks bonded ?

What prompts me to ask this is a an issue with an outboard in freshwater where I was advised to switch to a magnesium anode

Magnesium is the recommended anode material for use in freshwater. Zinc and aluminium both form oxide layers making them ineffective.
Magnesium is too reactive for use in salt or even brackish water.
Aluminium anodes ( an alloy containing a small % of indium), are suitable for brackish or salt water.
Zinc is suitable for salt water and some sources say also brackish water.

Not at all sure about not being able to protect brass with zinc anodes.

Brass may contain zinc as an alloying element but it is not present as free zinc but rather as a solid solution of zinc in copper. Nominal 60/40 brasses have a composition consisting of two solid solutions of different composition. They tend to be more susceptible to dezincification. ( due to them consisting of two phases ??) The structure can be considerably modified by cold working and heat treatment. I understand that heat treatment is an essential part of the production of dezincification resistant brass, which is a leaded high tensile brass that would otherwise be susceptible to dezincification.

Vyv knows much more than I do about the metallurgy but the phase diagram for copper and zinc explains the basics

As you can see copper and zinc form a whole series of solid solutions right across the nearly full % range.

 

[fergie_mac66]

alumin anodes

Thank you Tranona&VicS seems I may be better with an aluminum anode for the outboard.

I realize seacocks are not normally bonded , On both my westerly and the cat the seacocks are not bonded . The outboard issue had me wondering whether they should be.

 

[yacht surveyor]

....What is more concerning is the silence from your own professional body, the YBDSA. I can appreciate why no individual insurance broker or surveyor would want to put his head above the parapet, preferring to leave that to someone else, and you have done this community a signal service by your own actions in this regard.

Might I suggest that a joint statement of 'best practice' between your professional body and the main insurers active in the UK leisure boating market - published by your favourite sailing mag - might do much to repair the damage to reputation....?

Thanks for posting this. I was not clear where you found it, but it was interesting to read.

The YDSA did raise this with financiers and insurers earlier this year as a topic presented by the article's author at our Annual City Conference. This was not done with a public fanfare, (which many may perceive as "silence") but a significant number of the key players in the industry were present and heard the message.

 

[Lady Campanula]

Your comments are appreciated, Martin, and we should be grateful to surveyor Paul Stevens and editor Paul Gelder for printing the 'brass seacocks' warning article in the June edition of YM.

Sailing as I do on the Tamar and adjacent waters, and aware of the sunken yacht ( one of several thereabouts ) in the magazine's picture just a stone's throw from a prominent boatyard, I became aware of the issue quite some months ago and also became aware that numerous 'professionals' had been aware of the problem for rather longer - but were keeping quiet about the issue. They certainly were not telling their clients......

Hence this Original Post here at the end of March/beginning of April.

We now have close on 4000 yottie readers of this thread, and however-many-thousands yottie readers of YM magazine, aware of the problem. So it's well out in the open...

I still think an open letter/joint statement of best practice, or at least a note of warning, from the YBDSA and the insurers' body - as previously suggested - might enhance the already high public regard in which both groups basks.

'Uberrimae fidei' cuts both ways in insurance law.....

 

[2Tizwoz]

I've just done a 'survey'. The boat I'm 'fettling' has 14 - yes, 14 - holes in the hull BTWL which could cause me grief.

And that's a little 'un, with nothing untoward on board.

Stern tube/cutless bearing
Anode bolts x 2
Cockpit drain x 2
Engine raw water intake
Sea toilet x 2
B&G sounder x 2
B&G log
Sink
Unused through-hull
Engine exhaust

That's a lot of potential trubl....




Here's some 'edited commentary' from some of the fallout, FWIW:



Er, don't hold your breath....

B & G through hulls are supposed to be either bronze or plastic. As what metal through hulls I have are over thirty years old hopefully they are bronze.

They do still look pretty much like new.

 

[jerry098]

Vetus brass fittings

I've just had a new engine fitted by a reputable boat yard. Not a cheap exercise and at no stage did I suggest they skimp on anything they thought needed changing or upgrading, especially when it was a matter of safety.
As part of this process they suggested that I replace the raw water intake skin fitting and sea cock. For this they used Vetus parts.
Upon reading the article in Yachting Monthly and reading this thread you can imagine I was rather surprised to see that they had chosen to use brass fittings (Vetus can supply either brass or bronze)
I've checked with Vetus and they assure me that the brass fittings they supply are of marine quality but can't tell me if they are DZR brass!
Upon taking this up with the yard they tell me they have fitted hundreds of brass skin fittings with no problems. They also say that if I chose to use bronze they would have to change all of the skin fittings as well as some may be brass.
My boat is a Moody and as standard they bonded all the skin fitting to the hull anode.
The boat is used solely on the sea.
What do you think I should do?
Thanks,
Jerry

 

[Tranona]

in general terms there is no need to bond skinfittings on a GRP boat as they are not in elecrtical contact with any other metal.

If you are worried about the new water intake replace it with a DZR from somebody like ASAP. They are not expensive - probably similar price to Vetus. A 3/4" fitting and ball valve are around £35. The original Moody fittings will almost certainly be DZR and may even be bronze if an older boat.

 

[vyv_cox]

The problem with 'marine quality' brass is that it doesn't mean anything. There are brass derivatives known as Admiralty Brass (also known as Admiralty Bronze) and Naval Brass which you might think were perfect, but they are just brass with a little bit of tin added. DZR is also brass but made in a very special way, plus a bit of arsenic. AFAIK DZR is always marked up as such on valves, either with DZR or CR, but skin fittings are not.

The only way to tell brass from DZR is by analysis. Brass can be told from bronze by its colour, bronze being more red.

Brass skin fittings are not going to fail in the short term so you don't really need to take action immediately. I would monitor them annually for dezincification when ashore.

I would not bond any skin fittings. Indeed, one of the first jobs I did when I bought my boat 15 years ago was to remove the bonding and hull anode that someone had added.

 

[Martin_J]

This 'CR' marking on fittings is very subtle isn't it... It's only when you know what you're looking for that you spot it.

Perhaps sbdy can post a pic because the CR letters are actually joined up and can look like an O with a squiggle. When the ball valve is mounted vertically.. hope you can see what I mean.

Found a link...
http://www.asap-supplies.com/marine/hull-mounted-water-strainers/ball-valve-dzr-female-each-end

 

[Martin_J]

At least if the letters are cast instead it is easy to read whether they say CW602N (and hopefully not CW617N).

 

[Stork_III]

This 'CR' marking on fittings is very subtle isn't it... It's only when you know what you're looking for that you spot it.

Perhaps sbdy can post a pic because the CR letters are actually joined up and can look like an O with a squiggle. When the ball valve is mounted vertically.. hope you can see what I mean.

Found a link...
http://www.asap-supplies.com/marine/hull-mounted-water-strainers/ball-valve-dzr-female-each-end

Here another view of "CR" page 2, but is it not a reversed D & R? http://www.copperinfo.co.uk/alloys/brass/downloads/is-36-dezincification-resistant-brass.pdf

 

[Martin_J]

Interesting thought.. Understood it to be short for 'Corrosion Resistant' though.

CR DR

 

[fergie_mac66]

Hot water systems

Wonder whether the use of brass in certain water area has caused hotwater accidents due to dezincing

 

[Boo2]

...mentions that Aquafax told MAIB they would tidy up their catalogue to help people avoid brass, yet here is their catalogue

In fairness the link here does categorise their fittings in terms of materials. Site seems to have hung up tonight though.

Boo2

 

[vyv_cox]

Wonder whether the use of brass in certain water area has caused hotwater accidents due to dezincing

Not sure about personal accidents but we have had leaks due to corrosion of brass fittings. 60/40 Brass is OK in hard water areas but in water like ours, very soft, it does corrode. I have had a couple of gate valve failures due to dezincification.