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Old 15-01-2014, 19:02   #1
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Identfying Bronze versus Brass

Is there a way to chemically test bronze and brass in order to tell them apart? Or is there any other sure fired way to tell which is which, other than the color.
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Old 15-01-2014, 19:24   #2
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Re: Identfying Bronze versus Brass

X-ray fluorescence (XRF) spectroscopy. You can buy a hand-held instruments like this: Handheld XRF Metal and Alloy Analyzers from Bruker | Bruker Elemental
It's likely to be expensive.
A destructive method would be to immerse a sample in salt water or acid and wait for the zinc to dissolve.
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Old 15-01-2014, 19:49   #3
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Re: Identfying Bronze versus Brass

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X-ray fluorescence (XRF) spectroscopy. You can buy a hand-held instruments like this: Handheld XRF Metal and Alloy Analyzers from Bruker | Bruker Elemental
It's likely to be expensive.
Take the suspect metals to a metal recycler, they should have an Alloy Analyzer

Quote:
A destructive method would be to immerse a sample in salt water or acid and wait for the zinc to dissolve.
Close but, that would take sometime, and will not provide any real information.

You could connect the metals with a silver half-cell and a very accurate digital multi-meter, drop em in salt water to about 3 feet.

Then measure the Mv on each metal.

Lloyd
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Old 15-01-2014, 19:57   #4
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Re: Identfying Bronze versus Brass

A qualitative observation of parts you might see and buy:

The bright yellow brass you find at Home Depot and other hardware stores can be counted on to be high in zinc. The comparison is to look at the well-cut threads in purpose built marine fittings such as Groco at West Marine will glow a bit red in the bright lights. Parts form reputable marine suppliers of "marine Bronze" will polish nicely to a golden hue but will never reach the brilliant yellow of the zinc rich (also cheap) stuff. Marine bronzes will/may also contain zinc put not as the primary alloying element.

Here is a seller of parts and raw materials with some pretty good short descriptions.

Open the TAB 'ABOUT COPPPER BRASS BRONZE'

McMaster-Carr
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Old 15-01-2014, 20:12   #5
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Re: Identfying Bronze versus Brass

I have a titanium pocket knife. I can stick the point into brass but bronze I can barely scratch. If it's a European boat ... Beneteau, Dufour, Jeanneau, Hanse, Bavaria etc. all the ball valves are brass, mostly chrome plated.
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Old 15-01-2014, 20:25   #6
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Re: Identfying Bronze versus Brass

The replies so far have mentioned cast products.

But how about screws, bolts and nuts? I guess you really have to trust the supplier... for your underwater parts?
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Old 15-01-2014, 20:29   #7
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Re: Identfying Bronze versus Brass

Just to muddy the waters a bit. Good marine brass is 85,5,5,5 also called red brass or gun metal. Gun metal as bronze cannon's on ships of old, were made of it.

So you had 85 percent copper, 5 percent tin, 5 percent lead and 5 percent zinc. Yellow brass on the other hand is 20-25 percent zinc or more. Avoid yellow brass in all raw water systems. Sometimes other metals are used depending on foundry, but the above is pretty standard.

Now a days, in the USA anyway, the 85,5,5,5 brass is not quite the same. This due to low lead (really no lead, but I degrees) code requirements in plumbing systems. So instead of lead, we now have 5 percent aluminum. Which is fine unless your running sea water through it.

So for all intents and purposes, we now have 10 percent sacrificial metal in salt water, due to micro-galvanic action. Which leaves 90 percent of good metal, not 95 percent as in days of old. Still better then 25% zinc, but not quite as good as the old stuff.

There are of course other bronze/ brass formulations out there, but 85,5,5,5 is pretty much what your going to fine in the marine stores.

Hardware stores might have a small selection of bronze, but most of it will be yellow brass. BTW anything over roughly 80 percent copper is generally considered bronze.
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Old 15-01-2014, 20:43   #8
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Re: Identfying Bronze versus Brass

I thank the OP for asking that question because I always wondered this myself...

I can tell stainless from other metals, but if I place an order for bronze bolts/whatever that will be used under the waterline. How do I know if they are bronze? I mean, I have them and I don't own a laboratory, all the sales guy knows is that this is "bronze".
Like I said before, do you rely on your vessel's integrity based on suppliers trust?
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Old 16-01-2014, 16:12   #9
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Re: Identfying Bronze versus Brass

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Originally Posted by SVTatia View Post
The replies so far have mentioned cast products.

But how about screws, bolts and nuts? I guess you really have to trust the supplier... for your underwater parts?
As I noted, cut metal such as threads will appear somewhat red. As for other materials, If you buy metal stocks from McMaster it will come with a lab analysis sheet. If you buy fasteners from Jamestown or McMaster or other marine supplier you will lilely be OK. Fasteners listed as 'brass' are not to be trusted.

If you are buying antique or old stuff salvaged, it either looks good & is OK or you will be able to tell.

SAILORCHIC34 touched on a hot button. The regulations for marine bronze in the US are tighter than in Europe. They operate on a planned mortality life of too finite a length. In the US we still have standards. If you replace seacocks in Europe, plan to do it again in a couple of years. I find this one really dangerous.
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Old 16-01-2014, 16:34   #10
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Re: Identfying Bronze versus Brass

Sailorchic,
What do you do,or what was it you used to do for a living? I ask as your knowledge base is unusual
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Old 16-01-2014, 16:58   #11
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Re: Identfying Bronze versus Brass

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Sailorchic,
What do you do,or what was it you used to do for a living? I ask as your knowledge base is unusual
I am a Professional Mechanical Engineer. I design custom specialty machinery from tiny stuff to 6000 HP test dynamometers. I used to work for a major chemical company where we needed a lot of special metals. I studied corrosion engineering in a previous life. Even now, we ponder the metallurgy of many of our parts and machines.

Recently, we replaced all of the really old 1-inch iron pipe with red bronze valves in our 5 SS diesel tanks with new SS pipes and new red valves. The tanks - BSPT threads. I had to make all of the new tank stubs in our machine shop. Convenient access to a major machine shop is great for a restoration on a 30 year old boat. Main chainplates replaced with GR5 titanium. No more inspections - ever.

We plan to retire, sell all the dirt stuff, move aboard and leave by the St Lawrence in 1 - 2 years.
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Old 16-01-2014, 17:08   #12
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Re: Identfying Bronze versus Brass

Little confused how I ask one person but get answered by another, but no matter.
I had noticed you had "dirty hands, mechanic type" of knowledge that is rare among Engineers, but also had way more metallurgical knowledge than almost any mechanic.
I mean this as a complement
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Old 16-01-2014, 17:24   #13
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Re: Identfying Bronze versus Brass

Sorry, I'm the confused one. I thought you meant me. I built RC & gas planes as a kid, built a house, restored a car & rebuilt engines. Engineering pays better than mechanic - most times & I only get dirty when I need to.
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Old 16-01-2014, 18:10   #14
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Re: Identfying Bronze versus Brass

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I have a titanium pocket knife. I can stick the point into brass but bronze I can barely scratch. If it's a European boat ... Beneteau, Dufour, Jeanneau, Hanse, Bavaria etc. all the ball valves are brass, mostly chrome plated.
The ability of your knife to scratch brass will probably vary with the particular alloy & the heat treat. I find half hard brass difficult to engrave. Full hard brass is an even tougher beast to mark.

There are many flavors of both brass & bronze. Their properties vary quite a bit.

Brass is an alloy of copper & zinc. Bronze is an alloy of copper & tin. Other elements may be included in either alloy. Their are also alloys of copper, tin & zinc that carry a variety of titles.

I'm not sure why the OP want's to identify a metal as brass or bronze. It may be more useful to determine if the item he has is suitable for the use he intends.
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Old 17-01-2014, 07:23   #15
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Re: Identfying Bronze versus Brass

Your local scrap yard may have a Niton x-ray fluorescence (XRF) analyzer, (Niton gun) which can identify/differentiate (non-destructive) nickel, copper, titanium, and aluminum alloys (& more).
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