Checking through hulls have not turned to copper

[tudorsailor]

When I bought our yacht 5 years ago I accompanied the surveyor all day. One thing he did was to scrape a bit of anti-foul off each through-hull and look to see if the brass was turning to copper. He found one that was and it was replaced.

The yacht is currently out of the water and not yet re-antifouled. Should I go around with a penknife or even a wire brush to check every though hull?

How often should one do this check?? Why is the change from brass to copper bad? Will it loosen?

Thanks

TudorSailor

 

[snowleopard]

How often should one do this check?? Why is the change from brass to copper bad? Will it loosen?

If you take out the zinc from brass you leave a sponge-like matrix of copper which has no mechanical strength so it could snap off with the slightest impact leaving a big hole in the hull.

BUT - You shouldn't be using brass for below-waterline through-hulls. The correct material is bronze which is pretty much immune to dezincification, most bronzes don't actually contain any Zinc.

If your fitting is brass, look for an area that is pink rather than gold coloured and can be scored with a knife.

 

[Chrissie]

Yes absolutely, scrape back the anti foul and examine the metal for any signs of it going pinkish, every time you get the opportunity.

 

[tudorsailor]

If you take out the zinc from brass you leave a sponge-like matrix of copper which has no mechanical strength so it could snap off with the slightest impact leaving a big hole in the hull.

BUT - You shouldn't be using brass for below-waterline through-hulls. The correct material is bronze which is pretty much immune to dezincification, most bronzes don't actually contain any Zinc.

If your fitting is brass, look for an area that is pink rather than gold coloured and can be scored with a knife.

Found a photo from 2006

Ah now you have exposed my ignorance. You are probably right that the fittings are bronze not brass. Having said that, there was still a change in metal to expose pink copper. So I guess I still need to have a scrape?

Tudor
Sailor

 

[Babylon]

Don't pussy around with just a wire brush, use an engineer's file to file the face down through the pink surface to expose what's underneath - that's what the engineer suggested I do when I trashed my own seacocks (see my recent PBO thread).

 

[KristiferColumbus]

When I bought our yacht 5 years ago I accompanied the surveyor all day. One thing he did was to scrape a bit of anti-foul off each through-hull and look to see if the brass was turning to copper. He found one that was and it was replaced.

The yacht is currently out of the water and not yet re-antifouled. Should I go around with a penknife or even a wire brush to check every though hull?

How often should one do this check?? Why is the change from brass to copper bad? Will it loosen?

Thanks

TudorSailor

I would be very surprised if the builder of that flashy yacht pictured in your avatar used brass.They are I believe a quality yacht builder & I can't imagine any such builder using brass in that situation.I would check with them & see what they say.I would be very very surprised if they used brass!

 

[KristiferColumbus]

Found a photo from 2006

Ah now you have exposed my ignorance. You are probably right that the fittings are bronze not brass. Having said that, there was still a change in metal to expose pink copper. So I guess I still need to have a scrape?

Tudor
Sailor

The picture you have posted looks perfectly alright & nothing to worry about to me.Far from it it looks practically brand new!Stop worrying.

 

[Paul_G]

there is an article about this in the June YM. Interestingly the RCD rules and ISO means the seacocks only have to be good for 5 years allowing brass to be fitted.

 

[KristiferColumbus]

there is an article about this in the June YM. Interestingly the RCD rules and ISO means the seacocks only have to be good for 5 years allowing brass to be fitted.

Who are the RCD?I presume that ISO stands for International Standards Organization?
Brass is a nasty metal that not only age hardens & brakes down in a salt water environment but it brittle & subject to cracks at the best of times.....You use it if you want to I would'nt touch it with a barge pole!

 

[penfold]

there is an article about this in the June YM. Interestingly the RCD rules and ISO means the seacocks only have to be good for 5 years allowing brass to be fitted.

More evidence that RCD is a complete waste of everyone's time.

 

[vyv_cox]

I would be very surprised if the builder of that flashy yacht pictured in your avatar used brass.They are I believe a quality yacht builder & I can't imagine any such builder using brass in that situation.I would check with them & see what they say.I would be very very surprised if they used brass!

Sorry then, you are going to be surprised! IIRC Lady Campanula highlighted this issue on PBO not long ago and YM are about to run a campaign on it, kicked off in the June issue. Many builders are using brass skin fittings and seacocks because the guidelines say they only have to last for five years.

Examples of dezincification can be seen on my website at http://coxengineering.co.uk/BandB.aspx

 

[AntarcticPilot]

Who are the RCD?I presume that ISO stands for International Standards Organization?
Brass is a nasty metal that not only age hardens & brakes down in a salt water environment but it brittle & subject to cracks at the best of times.....You use it if you want to I would'nt touch it with a barge pole!

No, it stands for ISO. ISO isn't an acronym; it is the short form of the name of the organization. This is to avoid the usual problem of acronyms being different in different languages (ISO would probably be OIS in French, for example).

ISO was chosen to mean equal. Of course, it's origins are in the acronym, but the official name of the organization is ISO.

 

[Paul_G]

Who are the RCD?I presume that ISO stands for International Standards Organization?
Brass is a nasty metal that not only age hardens & brakes down in a salt water environment but it brittle & subject to cracks at the best of times.....You use it if you want to I would'nt touch it with a barge pole!

The RCD is the EU Recreational Craft Directive of 1998, the one that defines classes A B C D etc. The standard for seacocks and through hull fittings is ISO 9093-1. All the info is in YM June edition

I don't suggest the use of brass, just that modern boat builders build to standards and ISO 9093-1 allows the use of brass sea cocks as it defines the "life" of the component as 5 years, and brass may just survive that long even if the boat is still in its infancy ( and just about to sink due to corroded sea cocks )

My boat is 30 years old and predates both RCD and ISO.

 

[KellysEye]

If you want to stop the problem replace bronze with Marelon throughulls. They are made of very hard nylon and are used on metal boats.

 

[Tranona]

If you want to stop the problem replace bronze with Marelon throughulls. They are made of very hard nylon and are used on metal boats.

However, as the YM article points out, they may not have the fire resistance for use in engine rooms. But of course this may be a moot point as plastic water supply hoses are allowed!

 

[paulstevens]

not really, the logic is that whilst even a small engine fire can damage the plastic hoses provided you can still close the metal seacock or valve after the fire is out you will stay afloat.

 

[Martin_J]

Interesting point Paul...

Does this then bring up the question as to whether or not the engine cooling water seacock should be in the engine bay?

If it is in the engine bay and an engine fire starts, maybe you will not be able to get to it to turn it off whether it is metal or not... Should it therefore be outside.

Or.. Do engine hoses filled with water not burn through so quickly.

Edit - Just re-read your post.. says 'so long as you can close the valve after the fire is out'. Not sure if my question above still stands.

 

[paulstevens]

Interesting point Paul...

Does this then bring up the question as to whether or not the engine cooling water seacock should be in the engine bay?

If it is in the engine bay and an engine fire starts, maybe you will not be able to get to it to turn it off whether it is metal or not... Should it therefore be outside.

Or.. Do engine hoses filled with water not burn through so quickly.

Edit - Just re-read your post.. says 'so long as you can close the valve after the fire is out'. Not sure if my question above still stands.

Yes Martin your point stands. Ideally the valve should be outside the engine space, but quite often its not, and cockpit drains are very often in there too. By definition the engine valve will be open if there is an engine fire, and the cockpit drains will always be open, so all those hoses are vulnerable to fire damage. Only the part below waterline has any resistance being full of water. In practice the hose will go floppy above this and fall downward allowing water to flood in, or in fires of longer duration simply melt at the waterline.
The MCA code asks for all flexible hoses to be of ISO 7840 fire resistant type, or lagged with protective material, or the valves operable from outside the engine space. Of course most boats do not need to be coded and as far as I can recall the useless RCD is silent on this but I may be wrong. Back on the original point MCA does not allow plastic seacocks in engine spaces. However some may argue this (cant think what for) because it actually says they must be of fire resistant materials, and Marelon does have some fire resistance, but each to their own.
Auto heat triggered extinguishers are an obvious safeguard, but make sure the extinguishent doesn't wreck the engine in just a small fire and hinder safe passage. Failing this a small aperture to insert a manual extinguisher into is good and most new boats are provided with this. Above all the last thing to do is open up the space allowing a huge rush of oxygen to the fire which will rapidly intensify and spread.
Getting off the point here but I look forward to the YM crash test fire with relish! The whole concept of making us all confront worst case scenario is brilliant IMHO.

 

[sighmoon]

If you want to stop the problem replace bronze with Marelon throughulls. They are made of very hard nylon and are used on metal boats.

Doesn't nylon absorb water and swell?

 

[paulstevens]

Doesn't nylon absorb water and swell?

yes, bit of confusion here, Marelon is not nylon it is glass reinforced Dupont Zytel. The Nylon fittings used in their thousands above the waterline are plain unreinforced material. In my experience though all the manufacturers and suppliers make it clear that they are for use above the waterline only.