banana
New member
any idea what this is.
Cheers
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Cheers
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marine brass?
- Thread starter banana
- Start date
ccscott49
Active member
I think it means "anti dezincification brass" Which does de-zinc anyway, but slower, brass is not a marine use metal, unless inside or above the waterline but even then its rubbish! Bronze, (real bronze, without zinc in it) is the only real marine stuff, which can look like brass, if that makes sense.
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penultimate
New member
Presume this is 60/40 Naval Brass (actually 61.7% Cu, 36.9% Zn, 1.4% Sn). I believe there are about 10 different brasses, the next most common probably being 70/30 Cartridge Brass.
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macd
Active member
Absobloodylutely. The entire isssue is a scandal, not helped by evasive descriptions like 'Tonval'. Viz the MAIB report on the flooding of charter fishing vessel Random Harvest near Brighton on 3 July 1999. The boat almost sank when a skin fitting failed. Amongst the reports findings:
"The use of trade names such as "Tonval" conceals rather than conveys the nature of the material used for the through-hull fittings."
"The material used for the fitting was unsuitable because of its susceptibility to dezincification."
The report recommended "that 'Tonval' be clearly and unambiguously identified as 'brass (not inhibited against dezincification)' in their sales literature.
The company which supplied the fitting dutifully promised to withdraw Tonval items from stock (or clearly label them, can't remember which). Unfortunately its name was Sou'Wester, and it promptly went bust before carrying out its promise. So still you can see old Sou'Wester Tonval items in scores of chandleries.
In fact even many presumably high-turnover mail order chandlers seem to stock nothing else. Wouldn't wish a sinking on anyone, but paying for the consequences of a few catastrophic failures would do them a power of good. Forum rules forbid me from expressing my true feelings about them, but maybe it's time some of the boating mags highlighted what's going on. After all, you can't expect every boaty to be a metallurgist. Suppliers have a legal and moral duty to sell stuff 'suitable for purpose'. At present, many of them palpably do not.
There, always feel better for a rant of an evening...
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"The use of trade names such as "Tonval" conceals rather than conveys the nature of the material used for the through-hull fittings."
"The material used for the fitting was unsuitable because of its susceptibility to dezincification."
The report recommended "that 'Tonval' be clearly and unambiguously identified as 'brass (not inhibited against dezincification)' in their sales literature.
The company which supplied the fitting dutifully promised to withdraw Tonval items from stock (or clearly label them, can't remember which). Unfortunately its name was Sou'Wester, and it promptly went bust before carrying out its promise. So still you can see old Sou'Wester Tonval items in scores of chandleries.
In fact even many presumably high-turnover mail order chandlers seem to stock nothing else. Wouldn't wish a sinking on anyone, but paying for the consequences of a few catastrophic failures would do them a power of good. Forum rules forbid me from expressing my true feelings about them, but maybe it's time some of the boating mags highlighted what's going on. After all, you can't expect every boaty to be a metallurgist. Suppliers have a legal and moral duty to sell stuff 'suitable for purpose'. At present, many of them palpably do not.
There, always feel better for a rant of an evening...
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Graham_Wright
Well-known member
Do a search of the forum topics.
Having fumed about a brass (CZ121) stern tube from T Norris ("Everybody uses
CZ121, phosphor bronze is far too expensive") I posted a comment which provoked very responsible replies.
The material for my home made stern tube in phosphor bronze cost £1 more than the CZ121 equivalent.
I have opted for SS 316 fittings which I can buy from my local pipeline supplier cheaper than bronze and not much more than brass.
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Having fumed about a brass (CZ121) stern tube from T Norris ("Everybody uses
CZ121, phosphor bronze is far too expensive") I posted a comment which provoked very responsible replies.
The material for my home made stern tube in phosphor bronze cost £1 more than the CZ121 equivalent.
I have opted for SS 316 fittings which I can buy from my local pipeline supplier cheaper than bronze and not much more than brass.
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boatmike
Well-known member
I agree that critical skin fittings and valves should always be bronze. DZB has a use in that it is considerably cheaper for interior use on water and fuel lines and skin fittings above the waterline but should never be used for underwater skin fittings
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tugboat
New member
First class rant, that! /forums/images/icons/smile.gif
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AndrewB
Well-known member
Re: marine brass rant.
The problem is as much to do with the modern style of yachting as it is to do with the use of brass. Brass and bronzes with a high zinc content (e.g. manganese bronze) have been used for the underwater fittings of yachts for a long time, and until recently were fitted by quite reputable boat-builders. The rate zinc is leached from brass very much depends on electricity usage and grounding, and the proximity of dissimilar metals in and around the yacht. Both of these have risen considerably in recent years, partly as a result of a demand for much better quality accomodation aboard and for more powerful engines and stern gear. When I started sailing in the '70's, a decent brass underwater skin fitting might well last 10 years, now 3 is the limit.
Incidentally I've been told that the quality of the amalgam is also highly significant to longevity. This concerns how well the metals are mixed together, rather than the proportion of each metal in the brass. This is another reason why the cheap imported brass gate valves from Italy and China last far less well than did the earlier British made ones.
The problem is as much to do with the modern style of yachting as it is to do with the use of brass. Brass and bronzes with a high zinc content (e.g. manganese bronze) have been used for the underwater fittings of yachts for a long time, and until recently were fitted by quite reputable boat-builders. The rate zinc is leached from brass very much depends on electricity usage and grounding, and the proximity of dissimilar metals in and around the yacht. Both of these have risen considerably in recent years, partly as a result of a demand for much better quality accomodation aboard and for more powerful engines and stern gear. When I started sailing in the '70's, a decent brass underwater skin fitting might well last 10 years, now 3 is the limit.
Incidentally I've been told that the quality of the amalgam is also highly significant to longevity. This concerns how well the metals are mixed together, rather than the proportion of each metal in the brass. This is another reason why the cheap imported brass gate valves from Italy and China last far less well than did the earlier British made ones.
milltech
Active member
Re: marine brass? (thread hijack)
One used to see them walking the quayside at Poole in slingbacks a few years ago, but they seem to have disappeared. Different class of sailor these days?
<hr width=100% size=1>John
http://www.on-line-marine.com
One used to see them walking the quayside at Poole in slingbacks a few years ago, but they seem to have disappeared. Different class of sailor these days?
<hr width=100% size=1>John
http://www.on-line-marine.com
snowleopard
Active member
Re: marine brass? (thread hijack)
<they seem to have disappeared>
no, they are included in the standard inventory of all flybridge boats. just watch them coming out of chichester/portsmouth on a sunday morning. every one has a blonde beside the helm /forums/images/icons/wink.gif.
<they seem to have disappeared>
no, they are included in the standard inventory of all flybridge boats. just watch them coming out of chichester/portsmouth on a sunday morning. every one has a blonde beside the helm /forums/images/icons/wink.gif.
milltech
Active member
Re: marine brass? (thread hijack)
Where do I pay my cheque?
<hr width=100% size=1>John
http://www.on-line-marine.com
Where do I pay my cheque?
<hr width=100% size=1>John
http://www.on-line-marine.com
ccscott49
Active member
Sea water and brass=problems! Its as simple as that. The price difference is very small, (couldnt spell neglible) I use bronze, or 316 stainless, (even above the waterline) and have never had a fitting/skin fitting failure in 35 years. I will stick with what I've got and know, thanks. IMHO of course.
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isandell
New member
But some of the most well regarded seacocks/skin fittings (ie Blakes) are made from DZR Brass.
Ian
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Ian
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Ships_Cat
New member
Agree with that, and Blakes actually advertise the fact - dezincification inhibited manganese bronze (an alpha brass) is widely used in high quality components and high quality propellors and is not a problem at all.
In fact a propellor of inhibited manganese bronze on a high performance ss shaft, insulated from the engine, does not need anodes and will not suffer galvanic corrosion. That will get a scream from the marina myth makers but it is a fact /forums/images/icons/smile.gif - if corrosion is suffered on a "bronze" or "brass" prop it will either be electrolytic (not galvanic) in which case other things will be dissolving as well and is impossible to happen if the shaft is insulated from the boat, or it is not corrosion inhibited manganese bronze.
John
<hr width=100% size=1>I am the cat but I am only 6.
In fact a propellor of inhibited manganese bronze on a high performance ss shaft, insulated from the engine, does not need anodes and will not suffer galvanic corrosion. That will get a scream from the marina myth makers but it is a fact /forums/images/icons/smile.gif - if corrosion is suffered on a "bronze" or "brass" prop it will either be electrolytic (not galvanic) in which case other things will be dissolving as well and is impossible to happen if the shaft is insulated from the boat, or it is not corrosion inhibited manganese bronze.
John
<hr width=100% size=1>I am the cat but I am only 6.
ccscott49
Active member
All I will say is, blakes are now.
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boatmike
Well-known member
Well regarded? By whom?
Blakes make fittings in bronze too... I repeat, there is nothing wrong with DZB above the waterline but not below.
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Blakes make fittings in bronze too... I repeat, there is nothing wrong with DZB above the waterline but not below.
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boatmike
Well-known member
I am surprised to hear you confusing bronze with brass John
I don't know what is sold on New Zealand but I can assure you that what is sold as DZB over here is not Manganese Bronze. It is in fact usually a CZ132 alloy designated "dezincification resistant" in that it resists loss of zinc for a certain distance below the surface. Often the term "Tonval" is used which I believe (although I am not sure) is basically a modified duplex 60/40 alloy recognised as acceptable for through hull fittings although I believe it was first developed as a replacement for naval brass in boiler tubes. While Tonval is OK unfortunately there are many other fittings made in what is designated as DZB that are a fairly low grade hot stamped brass. Most gate valves (which in my opinion have no place on a boat anyway) sold here are made out of this "nominal" DZB. These are OK for domestic plumbing but not for valves on seacocks as many have found to their cost.
If you look at Blakes and other reputable manufacturers you will find that they make identical products in Tonval and Gunmetal Bronze. While there is an opinion that Tonval is acceptable below the waterline other forms of DZB are not and both are inferior to a "proper job" in bronze. I still believe that propellers, P brackets etc. and skin fittings and valves below the waterline should be bronze. Other stuff inside the boat Tonval if you must...
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I don't know what is sold on New Zealand but I can assure you that what is sold as DZB over here is not Manganese Bronze. It is in fact usually a CZ132 alloy designated "dezincification resistant" in that it resists loss of zinc for a certain distance below the surface. Often the term "Tonval" is used which I believe (although I am not sure) is basically a modified duplex 60/40 alloy recognised as acceptable for through hull fittings although I believe it was first developed as a replacement for naval brass in boiler tubes. While Tonval is OK unfortunately there are many other fittings made in what is designated as DZB that are a fairly low grade hot stamped brass. Most gate valves (which in my opinion have no place on a boat anyway) sold here are made out of this "nominal" DZB. These are OK for domestic plumbing but not for valves on seacocks as many have found to their cost.
If you look at Blakes and other reputable manufacturers you will find that they make identical products in Tonval and Gunmetal Bronze. While there is an opinion that Tonval is acceptable below the waterline other forms of DZB are not and both are inferior to a "proper job" in bronze. I still believe that propellers, P brackets etc. and skin fittings and valves below the waterline should be bronze. Other stuff inside the boat Tonval if you must...
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boatmike
Well-known member
Even 316 stainless is subject to crevice corrosion below the waterline... But I basically agree with you although as I have said elsewhere "Tonval" is acceptable though inferior to gunmetal bronze.
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Ships_Cat
New member
Hi Mike
No, I am not confused as I did not refer to CZ132.
I specifically referred to manganese bronze which definitely is a brass (as I suspect that you know) being an alloy of copper and zinc, its "bronze" moniker being a misnomer. I think in the British Standard it is probably CZ114 (a description not widely used in other parts of the world). It has manganese added to harden it and other things, typically including arsenic, in its alpha phase to make it dezincification resistant.
It is the brass which is commonly used for marine fittings, including for under water. For under water items, propellors are commonly manganese bronze (and those are high quality ones, if anyone's propellor has dezincified then it was not a dezincification resistant manganese bronze) as are "bronze" seacocks.
I think that the seacocks that people normally have available to them and regard as "bronze" (including Blakes) are actually a casting brass DZ1 which is then heat treated to provide dezincification resistance (by ensuring it is in the alpha phase I assume, but I stand to be corrected on that by a metallurgist).
So it is a dezincification resistant brass and as I set out in my earlier post is a widely used high performing brass for service in seawater. I would be quite confident it is what people often actually have when they believe that they are using a bronze.
John
<hr width=100% size=1>I am the cat but I am only 6.
No, I am not confused as I did not refer to CZ132.
I specifically referred to manganese bronze which definitely is a brass (as I suspect that you know) being an alloy of copper and zinc, its "bronze" moniker being a misnomer. I think in the British Standard it is probably CZ114 (a description not widely used in other parts of the world). It has manganese added to harden it and other things, typically including arsenic, in its alpha phase to make it dezincification resistant.
It is the brass which is commonly used for marine fittings, including for under water. For under water items, propellors are commonly manganese bronze (and those are high quality ones, if anyone's propellor has dezincified then it was not a dezincification resistant manganese bronze) as are "bronze" seacocks.
I think that the seacocks that people normally have available to them and regard as "bronze" (including Blakes) are actually a casting brass DZ1 which is then heat treated to provide dezincification resistance (by ensuring it is in the alpha phase I assume, but I stand to be corrected on that by a metallurgist).
So it is a dezincification resistant brass and as I set out in my earlier post is a widely used high performing brass for service in seawater. I would be quite confident it is what people often actually have when they believe that they are using a bronze.
John
<hr width=100% size=1>I am the cat but I am only 6.
boatmike
Well-known member
John,
I know we have a common respect for one anothers knowledge and I didn't mean to put this into doubt. In fact I agree with what you have said entirely, but I think we are both confusing the rest of the forum who may or may not know the difference between bronze and brass so let me start again in an attempt to clarify.
There are many alloys of copper and zinc that are nominally termed brass and bronze and many people are confused between the two terms. Neither term is definitive and there are many alloys of both and some that are variously called brass and bronze at the same time. It is indeed true that the distinction between them is a rather academic one and any form of bronze could actually be termed a brass alloy in fundamental terms.
To the layman yottie however, "bronze" usually means either manganese bronze which as you say is used for propellers and such like mainly due to it's high tensile strength and corrosion resistance or aluminium bronze which is more easily forged but not I believe, widely seen. I will touch on other forms of bronze later.
Brass usually is taken to be either Yellow brass or Red Brass, the difference being mainly the copper content that gives it its colour. Yellow circa 65% Red circa 85%
Using this distinction and forgetting props (which are nearly all manganese bronze as you say) one usually finds, on chandlers shelves in the UK, skin fittings in yellow brass and manganese bronze. It is the difference between these two alloys that is usually thought of as either brass or bronze. (leaving Tonvil aside for the minute)
Without attempting a treatise on alpha phase and duplex alloys lets just keep it simple and say that most manganese bronze is of a type formulated to resist de-zincification and it is possible to formulate yellow brass to resist de-zincification too. This brass is what is commonly called DZB. This material is found in many forms but is widly used for hot stamped (forged) gate valves and other parts including skin fittings. Valve bodies and skin fittings can also be obtained in both aluminium bronze, manganese bronze and phosphor bronze.
There are, again in general terms, two fundamental differences between the brass alloys and the bronze alloys (by the above destinction of which is which) That is that the bronzes have a tensile strength typically three times that of brass and the corrosion resistance of bronze is much higher than brass.
For this reason I still think bronze is the alloy of choice for below the waterline and brass (even dezincification resistant brass) should not be used in what is usually a fit and forget application (until it breaks that is. Then you remember!)
As far as the original question is concerned regarding "marine brass" there is no simple answer. Apart from straightforward ally-bronze and mang-bronze, there is also gunmetal and phosphor bronze that are excellent bearing materials but have a lower tensile strength and what traditionally has been known as "Naval Brass" or Tobin bronze which is I believe what we now know as "Tonvil" (I think this is true, anyone else confirm this is what Tonvil is please join in!)
Naval or Marine brass is circa 60%copper, 0.5-1.5%tin,0.3%lead, remainder zinc.
Tensile is about 60,000 psi (about twice that of yellow brass)
I have through time seen a lot of skin fittings made in gunmetal which is OK too but not as high tensile as manganese bronze.
All of the above is a generalisation and my opinion as a marine engineer. I am not a metallurgist. I therefore stand willing to be corrected on detail.
Therefore I still say fit bronze of whatever type below the waterline in preference to brass but would prefer it to be higher tensile manganese bronze for preference.
Hope you agree!
Mike
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I know we have a common respect for one anothers knowledge and I didn't mean to put this into doubt. In fact I agree with what you have said entirely, but I think we are both confusing the rest of the forum who may or may not know the difference between bronze and brass so let me start again in an attempt to clarify.
There are many alloys of copper and zinc that are nominally termed brass and bronze and many people are confused between the two terms. Neither term is definitive and there are many alloys of both and some that are variously called brass and bronze at the same time. It is indeed true that the distinction between them is a rather academic one and any form of bronze could actually be termed a brass alloy in fundamental terms.
To the layman yottie however, "bronze" usually means either manganese bronze which as you say is used for propellers and such like mainly due to it's high tensile strength and corrosion resistance or aluminium bronze which is more easily forged but not I believe, widely seen. I will touch on other forms of bronze later.
Brass usually is taken to be either Yellow brass or Red Brass, the difference being mainly the copper content that gives it its colour. Yellow circa 65% Red circa 85%
Using this distinction and forgetting props (which are nearly all manganese bronze as you say) one usually finds, on chandlers shelves in the UK, skin fittings in yellow brass and manganese bronze. It is the difference between these two alloys that is usually thought of as either brass or bronze. (leaving Tonvil aside for the minute)
Without attempting a treatise on alpha phase and duplex alloys lets just keep it simple and say that most manganese bronze is of a type formulated to resist de-zincification and it is possible to formulate yellow brass to resist de-zincification too. This brass is what is commonly called DZB. This material is found in many forms but is widly used for hot stamped (forged) gate valves and other parts including skin fittings. Valve bodies and skin fittings can also be obtained in both aluminium bronze, manganese bronze and phosphor bronze.
There are, again in general terms, two fundamental differences between the brass alloys and the bronze alloys (by the above destinction of which is which) That is that the bronzes have a tensile strength typically three times that of brass and the corrosion resistance of bronze is much higher than brass.
For this reason I still think bronze is the alloy of choice for below the waterline and brass (even dezincification resistant brass) should not be used in what is usually a fit and forget application (until it breaks that is. Then you remember!)
As far as the original question is concerned regarding "marine brass" there is no simple answer. Apart from straightforward ally-bronze and mang-bronze, there is also gunmetal and phosphor bronze that are excellent bearing materials but have a lower tensile strength and what traditionally has been known as "Naval Brass" or Tobin bronze which is I believe what we now know as "Tonvil" (I think this is true, anyone else confirm this is what Tonvil is please join in!)
Naval or Marine brass is circa 60%copper, 0.5-1.5%tin,0.3%lead, remainder zinc.
Tensile is about 60,000 psi (about twice that of yellow brass)
I have through time seen a lot of skin fittings made in gunmetal which is OK too but not as high tensile as manganese bronze.
All of the above is a generalisation and my opinion as a marine engineer. I am not a metallurgist. I therefore stand willing to be corrected on detail.
Therefore I still say fit bronze of whatever type below the waterline in preference to brass but would prefer it to be higher tensile manganese bronze for preference.
Hope you agree!
Mike
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