I'm glad you checked into the Kunifer thing. I found it very interesting =
and informative. I did some additional checking, too.
Alloys are wonderful things! The Kunifer or 90/10 copper/nickel alloy =
you're talking about is apparently known as C70600. It typically =
contains 10% nickel, with about 1.4% iron and 0.8% manganese, and now =
meets ASTM B466, SMMT C5B, ISO 4038, and SAE J1047 standards (in case =
anyone wants that information).
This alloy's yield strength is still about 40% lower than steel brake =
lines, its fatigue strength is about 50% lower than steel brake lines, =
and it is about 30% more subject to elongation. Burst pressure for =
C70600 was good...19,000 psi (just slightly below brazed steel lines at =
19,500 psi). They didn't list the burst pressure for seamless or welded =
steel lines, which should be even higher. Even at these lower strength =
ratings, it appears that the C70600 alloy is still more than adequate in =
terms of its overall specifications (if not quite as over-engineered as =
the steel lines).=20
It's main claim to fame (as you mentioned) is corrosion resistance. The =
copper-industry-supplied blurb that I was reading (at www.copper.org) =
claims that it is superior in corrosion protection to the coated (zinc, =
lead, tin, terne, epoxy, etc.) steel lines, which will eventually =
succumb to local breaks in the coatings that allow corrosion to set in. =
While the article avoided mentioning the corrosion resistance of newer =
steel brake line coatings, such as superterne, Zyncroterne, =
PVDF/ElectroZinc and Procoat 2000, I would have to agree that the =
Kunifer/C70600 alloy would have better long-term corrosion resistance =
than coated steel lines.
However, they did NOT actually claim that it had better corrosion =
resistance than STAINLESS STEEL lines. All they dared say was that =
stainless steel lines were "susceptible to localized pitting and crevice =
corrosion especially in chloride-containing environments." Of course, =
they didn't say how rapidly the "pitting" would develop, how deep it =
would be, how concentrated the chlorides had to be, what chlorides were =
involved, what stainless steel alloy it was, or even whether it would =
even cause an eventual failure! Apparently, the corrosion resistance of =
stainless steel brake lines is good enough to make them worry about the =
competition and water down their claims to mere weak implication. From =
what I've read about stainless steel corrosion, crevice corrosion is a =
comparatively greater problem than pitting corrosion anyway, and =
something as structurally simple as steel tubing should be able to be =
manufactured without crevices (I don't know if the fitting joints would =
be considered 'crevices' here or not). At any rate, considering the =
source (copper industry) and their vested interests, I'd certainly =
suggest more homework on this, especially since there are several =
manufacturers and suppliers, such as PST, who offer stainless steel =
brake lines with a 20-year warranty! I've even heard of lifetime =
warranties on stainless lines, and I'll try to track down the =
supplier(s).
All in all, though, it sounds like brake lines made of Kunifer (and =
similar alloys) would be just fine. In fact, without doing more =
research, I'd have a hard time deciding between them and stainless =
steel.
HOWEVER, make NO mistake, nobody should EVER install ordinary copper =
tubing for brake lines!!! I would caution people NOT to go down to the =
local hardware store and buy a roll of copper tubing in the plumbing =
department and use it for brake lines! If there are approved =
copper-based ALLOYS that meet the specs, that's another thing. If anyone =
uses non-approved copper tubing for brake lines and has an accident as =
the result of brake line failure, they should expect big legal problems. =
Ordinary copper tubing is FAR weaker than these high-tech alloys.
Regards,
Alan Bowes
(Salt Lake City, Utah)
-----Original Message-----
From: CHAZ [SMTP:chaz.mackenzie@virgin.net]
Sent: Thursday, August 07, 1997 3:20 PM
To: mil-veh@skylee.com
Cc: alan_bowes@phast.com
Subject: RE Brake lines
Hi Alan, just for interest I went out and bought a roll of Kunifer
(copper/nickel 90/10)brake pipe and a roll of copper brake pipe
made by a different manufacturer.Both claim to meet BS 2871 part2=20
and to conform to international brake tubing spec ,the working=20
pressures are 3200psi and 3100psi .Bursting pressure is 17000psi !!
The " Ate Brake Design, Calculation, Testing " handbook gives the=20
"Booster run out point" as 840 > 1540 psi .If the system can only supply
about half the working pressure of the pipe that seems fairly safe to =
me.
I'm not trying to convince you to use copper/nickel rather than steel ,
thats up to you but fit copper/nickel and it's there forever , fit steel =
and replace it in a few years due to rust.
CHAZ 42 MB
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