Corrosion on aluminum antenna
 

I just bought a very old, verticle antenna. The ant. is aluminum and
very coroded.

Is this just a cosmetic problem, or will the corosion affect the
radiation/reception of RF?

Since the insulation on wire antennas doesn't affect their
effectiveness, I'm thinking the corosion wouldn't be a problem; but my
working-class logic has gotten me in trouble before. G

Will painting an aluminum antenna decrease it's effectiveness, or not
matter?

Thanx-

Aluminum oxide is an excellent insulator.

"Bob Sawyer" wrote in message
...
I just bought a very old, verticle antenna. The ant. is aluminum and
very coroded.

Is this just a cosmetic problem, or will the corosion affect the
radiation/reception of RF?

Since the insulation on wire antennas doesn't affect their
effectiveness, I'm thinking the corosion wouldn't be a problem; but my
working-class logic has gotten me in trouble before. G

Will painting an aluminum antenna decrease it's effectiveness, or not
matter?

Thanx-

Bob Sawyer wrote:
"I`m thinking the corrosion wouldn`t be a problem;--"

I think Bob is right.

Paint doesn`t help much, but it doesn`t hurt. You never see a new
microwave dish that isn`t painted before shipment, mostly for
appearance, but the paint inhibits corrosion too.

Aluminum spontaneously and rapidly forms oxide on its surface from
contact with air. Surface oxide is a barrier to further oxidation. A
painted dish is already oxidized before it is painted.

Rapid oxidation was one of the problems with aluminum house wiring.
Sound electrical connections were hard to make and keep. Depending on
the alloy, aluminum oxide (alumina) has such a high resistance that it
is used as an insulator at high temperatures. Fretting corrosion is
caused by interaction of aluminum with other metals and creates
corrosion problems (extreme resistance) at junctions.

Aluminum is a satisfactory material for antennas. Witness the millions
of outdoor TV antennas. High resistance of the thin oxide coating is not
incapacitating.

Best regards, Richard Harrison, KB5WZI

On Mon, 5 Sep 2005 09:16:24 -0500, John N9JG wrote:
"Bob Sawyer" wrote:
I just bought a very old, verticle antenna. The ant. is aluminum and
very coroded.

Is this just a cosmetic problem, or will the corosion affect the
radiation/reception of RF?

Since the insulation on wire antennas doesn't affect their
effectiveness, I'm thinking the corosion wouldn't be a problem; but my
working-class logic has gotten me in trouble before. G

Will painting an aluminum antenna decrease it's effectiveness, or not
matter?

[ Incidious top-posting corrected ]

Aluminum oxide is an excellent insulator.

And, for more than a century, folks have been radiating RF through
insulators. What did THAT have to do with the OP's question?

Yes, it is surprising how a piece of junk can still radiate a signal.

"drwxr-xr-x" wrote in message
...
Aluminum oxide is an excellent insulator.

And, for more than a century, folks have been radiating RF through
insulators. What did THAT have to do with the OP's question?

You and Bob are correct. However, I do hope the previous owner of the
antenna used an anti-seize compound on the joints, or else the new owner
will have a dickens of a time taking the antenna apart.

"Richard Harrison" wrote in message
...
Bob Sawyer wrote:
"I`m thinking the corrosion wouldn`t be a problem;--"

I think Bob is right.

Paint doesn`t help much, but it doesn`t hurt. You never see a new
microwave dish that isn`t painted before shipment, mostly for
appearance, but the paint inhibits corrosion too.

"Bob Sawyer" wrote in message
...
I just bought a very old, verticle antenna. The ant. is aluminum and
very coroded.

Is this just a cosmetic problem, or will the corosion affect the
radiation/reception of RF?

The only point at which corrosion will affect the performance of the antenna
is if the corrosion has gotten into any of the mechanical joints of the
antenna. Corrosion on the elements will not be a factor.



Since the insulation on wire antennas doesn't affect their
effectiveness, I'm thinking the corosion wouldn't be a problem; but my
working-class logic has gotten me in trouble before. G

Will painting an aluminum antenna decrease it's effectiveness, or not
matter?

Matters not a bit.

Jim

The main worry with oxidation is at the joint(s).
Clean the connections where the transmission lines are attached - and if the
antenna consists of more than one section, clean and penetrox the joints
where they are connected.
Otherwise, a little cosmetic oxidation shouldn't hoit. ;-)
I'm not sure about comic oxidation or cosmic oxidation.

"Bob Sawyer" wrote in message
...
I just bought a very old, vertical antenna. The ant. is aluminum and
very corroded.

Is this just a cosmetic problem, or will the corrosion affect the
radiation/reception of RF?

Since the insulation on wire antennas doesn't affect their
effectiveness, I'm thinking the corrosion wouldn't be a problem; but my
working-class logic has gotten me in trouble before. G

Will painting an aluminum antenna decrease it's effectiveness, or not
matter?

Thanks

Bob -

If you wish to clean the aluminum - lye (NaOH) is often used - however this
is a caustic agent - and usual precautions should be used if you use this
approach. There are also aluminum cleaners available at your local auto
supply stores.

Although some amateur use steel wool pads -- this can leave steel slivers on
the aluminum tubing that can oxidize (rust) - I refer non metallic scrubbing
pads if you need some elbow grease.

w9gb

Scothbrite pads seem to work great for cleaning off oxidation from
aluminum...when reassembling the joints, one can use penetrox (as
someone else mentioned) or alnox, both should be available at electrical
supply outlets.

Scott
N0EDV

gb wrote:

"Bob Sawyer" wrote in message
...

I just bought a very old, vertical antenna. The ant. is aluminum and
very corroded.

Is this just a cosmetic problem, or will the corrosion affect the
radiation/reception of RF?

Since the insulation on wire antennas doesn't affect their
effectiveness, I'm thinking the corrosion wouldn't be a problem; but my
working-class logic has gotten me in trouble before. G

Will painting an aluminum antenna decrease it's effectiveness, or not
matter?

Thanks


Bob -

If you wish to clean the aluminum - lye (NaOH) is often used - however this
is a caustic agent - and usual precautions should be used if you use this
approach. There are also aluminum cleaners available at your local auto
supply stores.

Although some amateur use steel wool pads -- this can leave steel slivers on
the aluminum tubing that can oxidize (rust) - I refer non metallic scrubbing
pads if you need some elbow grease.

w9gb

I just bought a very old, vertical antenna. The ant. is aluminium
andvery corroded.
Is this just a cosmetic problem, or will the corrosion affect the
radiation/reception of RF?
Since the insulation on wire antennas doesn't affect their
effectiveness, I'm thinking the corrosion wouldn't be a problem; but my
working-class logic has gotten me in trouble before. G Will painting
an aluminium antenna decrease it's effectiveness, or not
matter? Thanks

Bob -

If you wish to clean the aluminium - lye (NaOH) is often used -
however this
is a caustic agent - and usual precautions should be used if you use this
approach. There are also aluminium cleaners available at your local auto
supply stores.

Although some amateur use steel wool pads -- this can leave steel
slivers on
the aluminium tubing that can oxidize (rust) - I refer non metallic
scrubbing
pads if you need some elbow grease.

Hmm. Grey matter being a bit thin now, and about 40 years since I was at
school, but doesn't caustics on aluminium cause dangerous gases? Better
to use a scotch bright pad and an agent like Brasso (English name for
Brass cleaner compound) Once you've tin worm it's hard to stop the
oxydization. Your main priority is making sure the antenna has no
weaknesses in the wall thickness so that it's safe and will not bend.
Painting should have no detrimental electrical effects providing the
paint has no metalic compounds in it, but surly painting is just hiding
defects!! A previous posting asked about using stainless steel fixings
on aluminium, this causes an electrolitic conversion between the two
metals, not quite a good combination especially if you've shelled out
mega bucks for a decent antenna. After a few years in the air without
inspection you's be in for a big surprise.
Cheers from England. Dave

--
Amateur Radio Call Sign M1BTI, Located in Manchester England.
Locator square IO83TK
Chairman Of Trafford Radio Club. Club Call Signs G0TRG & M1BBP
Located at Umist, University Of Manchester Institute For Science And
Technology
Share What You Know, Learn What You Don't.

On Sat, 10 Sep 2005 19:02:39 +0100, Dave Piggin
wrote:

Once you've tin worm it's hard to stop the oxydization.

Hi Dave,

Is tin worm like White Pine Weevils or Bronze Birch Borers?

When a neighbor saw me laying out a ground field, he asked what I was
doing. I answered that I was doing root propagation to grow an
aluminum tree.

73's
Richard Clark, KB7QHC

Is tin worm like ... Bronze Bitch Borers?


I've met a few of them in my time...

Jim