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



"Cecil Moore" wrote in message
...
I'm no metallurgist so forgive my ignorance. Most of
us have had the problem of interfacing copper to
aluminum. Is there some sort of alloy terminal block
that will accomplish that feat? Seems simple enough
to create an alloy that gradually transitions from
copper to aluminum but what do I know?

1. I encountered dissimilar metal parts which had been joined by what was
termed "explosive welding" and/or "explosive bonding" both of which terms
show up nicely in Google.

In my case, the parts were cylindrical sleeves, the top of each being
stainless steel and the bottom being aluminum. I only saw one (out of
thousands) with the bond fractured and I don't know what hit it to break
it.
They seem quite strong.

Perhaps a vendor of such products has something you can use.

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
"


73, Barry WA4VZQ