I did a search for "tonval" on the matweb site, but could not find anything.

I have seen that advertised by some of the UK marine harware suppliers as
being dezincification resistant.
But I am not sure whether it is really suitable for seawater intakes.

Whadya think?

garry



"Jim Woodward" jameslwoodward at attbi dot com wrote in message
...
I agree completely that the terminology is a mess, but have a few
quibbles:

"Glenn Ashmore" wrote in message
news:hNXpb.1044$62.448@lakeread04...

snip

There is no real way without chemical analysis to determine the exact
alloy but the terms "brass" and "bronze" have no real engineering basis.

I completely agree -- two of the most misunderstood words in boating are
"brass" and "bronze". And, as noted below, it's even worse than you think.

With the exception of silicon and some aluminum bronzes, all bronzes
have some zinc in them. To add to the confusion, some bronzes have more
zinc in them that some brasses do.

The only thing I can figure out is that the "true" brasses have copper
and zinc but no tin. If a bronze alloy contains any zinc it also
contains some tin.

This might be true of bronzes used in marine applications, but it over
generalizes. My ASM Metals Handbook lists
Commercial Bronze -- 90 Cu, 10 Zn
Jewelry Bronze 87.5 -- Cu, 12.5 Zn

The tin evidently prevents dezincification. For
example "Naval or Admiralty Brass" is 60% copper, 39% zinc and 1% tin
but it is not subject to dezincification and is actually classified as a
bronze.

Apparently so.
Inhibited Admiralty -- 71 Cu, 28 Zn, 1 Sn
suggests this from the name and the ASM notes say, "Inhibitors are added
to
prevent dezincification" and give it good marks for corrosion resistance
for
sal****er velocities below 6 fps.

Red brass is also actually a bronze rather than a brass.

I don't understand why you say this is a bronze. The only ASM listing for
"Red Brass" is
Red Brass 85% -- 85 Cu, 15 Zn
The ASM doesn't show corrosion information, but mentions using it for heat
exchanger tubes. This material is also known as Red Brass (230).

The bronze that
Conbraco and other marine fitting companies use is actually red brass
C83600. 85% copper, 5% lead, 5% tin and 5% zinc. (That from a poster
who works in the casting department of a marine fittings company.)

Note that the lead doesn't do anything for us except that it makes it
easier
to machine and therefore cheaper (Hah!).

Yellow brass is a true brass at 63% copper and 37% zinc and highly
suseptable to dezincification. Common brass nipples are yellow brass.
Fortunately it is fairly easy to spot yellow and cartrige brass. Scrape
it with a file. Fresh yellow brass will have the characteristic bright
yellow gold color. Red brass will be more orange.

Roger Pretzer, Marine Metals Manual, International Marine, 1975, page 18,
says, "Brass with a high zinc content (over 16%) is subject to a type of
corrosion known as dezincification." He goes on to say that the color is a
good guide as follows:
red 5% zinc
bronze 5-10% zinc
gold 10-15% zinc
yellow 15% zinc

I'm not sure I can distinguish those subtleties, but it does suggest that
red is OK. And Red Brass 85% should be OK for our use.

For many more brasses and bronzes, but not a whole lot of useful
information
on corrosion, go to
www.matweb.com/

Getting back to your original question, I'm not sure that knowing that Red
Brass is probably OK in seawater will help. I'd still worry about
galvanic
action over time if you thread Red Brass into C83600 -- certainly the
voltage differences are very small, but they're working 24/7. This is why
we used PVC on Swee****er -- I ruled out the copper alloys because I
couldn't hope to find all the necessary bits in one alloy.



Jim Woodward
www.mvFintry.com


Keith wrote:
A hardware store near me carries what they claim are bronze pipe
nipples.
They are dark, not like yellow brass, except where they are threaded.
I
used
one to mount an aqualarm next to a strainer. I wish I could figure out
how
to verify that, short of a chemical analysis! If they really are
bronze,
they might be the only people in the USA that have them!

"Glenn Ashmore" wrote in message
news:6tRpb.999$62.845@lakeread04...

I am building a manifold to feed the washdown pump, air conditioning
cooling pump and watermaker bost pump. The supply is a 1 1/2" hose
coming from a 1 1/2" bronze seacock and Groco 970-1515 strainer.
Engine
cooling water is supplied through a 1" hose that comes off a
2"x1.5"x1"
Groco manifold at the strainer

I would use bronze reducing tees except that nobody makes bronze pipe
nipple. Only steel, brass or stainless. All three of which are not
acceptable. So I have decided to fabricate it from a length of 1"
wall
PVC tube with 1/2" threaded schedule 80 stubs for the valves.

Now comes the question of the valves themselves. I have some Conbraco
bronze ball valves that would work but my experience with them in the
past has not been all good. While the valve body is bronze the handle
is mild steel. On several deliveries of older boats the handles have
rusted to the point of being unusable and I have had to resort to Vice
Grips to operate the valve.

OTOH, I also have some Schedule 80 all PVC ball valves with stainless
handle retaining screws. I know that ABYC frowns on using PVC on
throughhulls but if the throughhull has a bronze seacock what are the
rules for down stream valves?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or
lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com





--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com