Another corrosion-inhibiting coating for aluminum is iridite. There are
conductive and non-conductive versions, something I learned the hard way
long ago.

Roy Lewallen, W7EL

axolotl wrote:
Jim Miller wrote:
there is another type of coating for aluminum called alodyne

which protects the same way as anodizing but is electrically
conductive.



Alodine (R) coatings are not conductive. You can specify a "type 3"
coating that is thin enough that fasteners will usually punch through
the coating layer.

See MIL-C-5541 chromate conversion coatings.

Kevin Gallimore

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On Sun, 10 Apr 2005 14:30:04 -0700, Roy Lewallen
wrote:

Another corrosion-inhibiting coating for aluminum is iridite. There are
conductive and non-conductive versions, something I learned the hard way
long ago.

Tell me about it [g].

I was the engineer responsible for transferring the design of the then
new Phoenix Missile IMPATT diode transmitter from the development lab
to the production floor.

The transmitter had three stages: a single diode driven by a
phase-locked Gunn oscillator fed a three diode cavity that drove a 16
diode cavity.

The development hardware used aluminum cavities that were comprised of
two pieces, with third copper piece that mounted the sixteen diodes.
So there was one aluminum-to-aluminum and one aluminum-to-copper
interface in each sandwich. Since this was a product for the U.S.
military, "passivation" was required for all aluminum parts.

I won't go into the considerable amount of detective work that it took
to decide that despite being "conductive" Alodine and its ilk are not
suitable coatings for rf components.

Gold is your friend, if of course, it's thicker than a few skin
depths, which is another long story. [g]


Roy Lewallen, W7EL

axolotl wrote:
Jim Miller wrote:
there is another type of coating for aluminum called alodyne

which protects the same way as anodizing but is electrically
conductive.



Alodine (R) coatings are not conductive. You can specify a "type 3"
coating that is thin enough that fasteners will usually punch through
the coating layer.

See MIL-C-5541 chromate conversion coatings.

Kevin Gallimore

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Amen! If gold did not exist, it would need to be invented just for EE
purposes. 73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Wes Stewart" wrote in message
...
snip


I won't go into the considerable amount of detective work that it took
to decide that despite being "conductive" Alodine and its ilk are not
suitable coatings for rf components.

Gold is your friend, if of course, it's thicker than a few skin
depths, which is another long story. [g]

"J. Mc Laughlin" wrote in message
...
Amen! If gold did not exist, it would need to be invented just for EE
purposes. 73 Mac N8TT

I've often entertained thoughts about the utility of gold in my other
hobby. I reload ammunition and cast lead bullets. Anything over 1200 to
1500 fps leads to leading from friction and gas cutting. Gold shares with
lead a high mass and malleability. Its higher melting point should allow
considerably higher velocities. Unfortunately I've not found suffient
quantities at economically feasible acquiral rates. Once Oklahoma gets its
lottery running and I win I'll get myself 4 or 5 pounds and find out if my
theory about gold bullets proves out. Another complication stems from the
high melting point which may prove damaging to my bullet molds. If that
should occur, I'll have to get someone to extrude me some gold rod and
lathe cut my gold bullets. Hmm, with gold rods, can gold ground plane
antennas for 2 and 6 meters be far behind? So many fun homebrew projects,
so little time, sigh.

Harold
KD5SAK