"NoSPAM" wrote in message
...
----- Original Message -----
From: "Sal M. Onella"
Newsgroups: rec.radio.amateur.antenna
Sent: Friday, November 07, 2008 11:20 PM
Subject: Aluminum to Copper interface


snip

2. I see a lot of brass and darn little corrosion. Would a transition
piece of brass be acceptable?

"Sal"

Red, yellow, and naval brass as well as aluminum bronze alloys are
marginally anodic with respect to copper so these alloys would provide
minimal corrosion protection. I know it might not be obvious, but steel
would make a better intermediate metal.

This will make sense if the actual voltages are included in the galvanic
series. These voltages are in sea water and with respect to a standard
calomel electrode.

Zinc -0.98
to -1.03
volts
Aluminum -0.70 to -0.90 "
Cast Iron -0.60 to -0.72
"
Steel -0.60
to -0.70
"
Red Brass, Yellow Brass, Naval Bross,
Aluminum Bronze -0.30 to -0.40 "
Copper -0.28 to -0.36
"

I saw those numbers decades ago -- in chem class, I guess. I cited brass
only because it seems to resist corrosion well, not because I actually know
what I'm talking about. g

73,
"Sal"
(actually KD6VKW)

"Sal M. Onella" wrote in message
...
I saw those numbers decades ago -- in chem class, I guess. I cited brass
only because it seems to resist corrosion well, not because I actually
know
what I'm talking about. g

Hi Sal,

As an instrumentation designer who worked mainly in the chemical industry,
corrosion abatement and material selection were daily facts of life. On
more than one occasion, the company metallurgists saved my rear end. For
example, stainless steel can be both cathodic and anodic with respect to
itself. While most folks consider stainless a panacea for corrosion
problems, it is not. In fact stainless alloys have little resistance to
salt water. There are many poor owners of stainless auto exhaust systems
that learn this the hard way when streets are salted in the winter to melt
ice. Copper, brass, and bronze alloys are used in marine environments
because of their anti-biofouling properties (barnacles, coral, mussels,
etc.).

I try to make my posts educational when I can. Thanks for telling me that
you had seen these numbers before. I hope they made a little sense this
time. I think if we all were back in school, we might pay more attention
this time. I know I would!

73, Barry WA4VZQ

"NoSPAM" wrote in message
...

snip

I think if we all were back in school, we might pay more attention
this time. I know I would!

Yup. A smarter man than I said, "We'll only need about five percent of what
we learned in college; too bad nobody knows which five precent."