"lagagnon" wrote in message
...
I am about to refurbish an old Hy-Gain TH3-Mk3 Thunderbird tri-band
yagi. This yagi has been used in a coastal environment and thus the
aluminum is slightly pitted and most of the connecting hardware needs
replacing.

I figure steel wool would work fine for the aluminum tubing, I know
how to test the traps, but I am wondering whether to use stainless
steel or galvanized hardware? Which would react least over time with
the aluminum? Also, I remember many years ago there is an electrical
joint compound stuff for using between the tubing sleeves - can anyone
please give me some brand names of this stuff?

Any other ideas appreciated....

Larry VE7EA

When I refurbished my TH-66DX about 10 years ago I used the green
"synthetic" steel wool or scotchbrite material.
Worked great and no residue left over.
Between the elements when put back together I used "never seize". Worked
well and conducts RF and DC.
After ten years I have not had any changes in the performance or SWR on the
antenna.

Sam - K7SAM

"lagagnon" wrote in message news:817062c5-
...

I am about to refurbish an old Hy-Gain TH3-Mk3 Thunderbird tri-band
yagi. This yagi has been used in a coastal environment and thus
the aluminum is slightly pitted and most of the connecting
hardware needs replacing.

I figure steel wool would work fine for the aluminum tubing, I
know how to test the traps, but I am wondering whether to use
stainless steel or galvanized hardware? Which would react least
over time with the aluminum? Also, I remember many years ago there
is an electrical joint compound stuff for using between the tubing
sleeves - can anyone please give me some brand names of this
stuff?

Any other ideas appreciated....

Larry VE7EA

Boy, the partial truths have been flying hot and heavy here. Allow
me to try to explain what is right and what is wrong...

You do _NOT_ want to use steel wool. Aluminum is anodic with
respect to steel. When you use steel wool, you imbed steel fibers
in the aluminum as many have noted. But what happens next is where
most posters are wrong. The aluminum around the steel fiber
corrodes protecting the steel from rusting. Thus your problem
becomes worse. Eventually the aluminum corrodes enough that it no
longer makes good electrical contact to the steel and the steel will
rust — or else fall out of the pit in the aluminum. You are left with
highly pitted aluminum.

I would suggest emery cloth, sandpaper, or a Scotchbright pad to
polish the aluminum. I would avoid stainless steel brushes too as
most grades of stainless are even more cathodic than steel with
respect the aluminum. Likewise avoid brass or copper brushes too.
For large areas, sand blasting works well if you use a fine sand and
not too much pressure.

As to hardware, I suggest hot-dipped galvanized bolts and nuts.
Zinc is slightly more anodic than aluminum, so neither material will
corrode much when in contact with each other. Hardware with a heavy
cadmium plating is also suitable, but due to the toxicity of cadmium
it is a little harder to find. Zinc-plated hardware offers minimal
protection because the zinc coating is so thin. If the hardware is
used in an application where minimal strength is needed, consider
aluminum hardware itself.

There are many joint compounds on the market for joining aluminum to
aluminum. Noalox and Penetrox are two common brands. These
compounds are typically a petroleum grease containing zinc particles.
These particles are usually produced by spraying molten zinc and air
through a nozzle. This produces small, irregular particles whose sharp
edges pierce the aluminum oxide surface film when the aluminum
pieces are tightly clamped together. This produces a good
electrical contact, and the zinc is very compatible with the
aluminum from a corrosion standpoint.

Whatever you do, avoid any contact of copper with the aluminum.
Where the transmission line connects, be sure and heavily coat any
copper solder lugs with solder. Try to keep a hot-dipped galvanized
washer between the lug and the aluminum.

Send me an email and I can send you some good articles on corrosion
that you might find interesting and informative. My experience
comes from many years working in the chemical industry. Even so, I
found the plant metallurgist to be a vital resource in material
selection for the instrumentation I designed.

--
73, Dr. Barry L. Ornitz WA4VZQ

Bruce wrote:
(Dave Platt) wrote in :

I figure steel wool would work fine for the aluminum tubing,
I've read that it is *not* a good idea to use steel wool to clean up
aluminum, especially if it's going to be exposed to the weather.
There's a tendency for tiny bits of the steel to get caught in the
aluminum... it'll rust.

I'd suggest using a 3M (or generic equivalent) green abrasive
scrubbing pad. These pads are rough enough to remove oxidation from
copper PC board material, so I imagine they'll shine up aluminum just
as well, but they won't leave rustable material behind.

Neverdull is far better to use.

http://www.nevrdull.com/



Isn't the oxide good? Doesn't it protect the metal?

On Apr 29, 2:38*am, wrote:
"lagagnon" wrote in message news:817062c5-

...





I am about to refurbish an old Hy-Gain TH3-Mk3 Thunderbird tri-band
yagi. This yagi has been used in a coastal environment and thus
the aluminum is slightly pitted and most of the connecting
hardware needs replacing.

I figure steel wool would work fine for the aluminum tubing, I
know how to test the traps, but I am wondering whether to use
stainless steel or galvanized hardware? Which would react least
over time with the aluminum? Also, I remember many years ago there
is an electrical joint compound stuff for using between the tubing
sleeves - can anyone please give me some brand names of this
stuff?

Any other ideas appreciated....

Larry VE7EA

Boy, the partial truths have been flying hot and heavy here. *Allow
me to try to explain what is right and what is wrong...

You do _NOT_ want to use steel wool. *Aluminum is anodic with
respect to steel. *When you use steel wool, you imbed steel fibers
in the aluminum as many have noted. *But what happens next is where
most posters are wrong. *The aluminum around the steel fiber
corrodes protecting the steel from rusting. *Thus your problem
becomes worse. *Eventually the aluminum corrodes enough that it no
longer makes good electrical contact to the steel and the steel will
rust — or else fall out of the pit in the aluminum. *You are left with
highly pitted aluminum.

I would suggest emery cloth, sandpaper, or a Scotchbright pad to
polish the aluminum. *I would avoid stainless steel brushes too as
most grades of stainless are even more cathodic than steel with
respect the aluminum. *Likewise avoid brass or copper brushes too.
For large areas, sand blasting works well if you use a fine sand and
not too much pressure.

As to hardware, I suggest hot-dipped galvanized bolts and nuts.
Zinc is slightly more anodic than aluminum, so neither material will
corrode much when in contact with each other. *Hardware with a heavy
cadmium plating is also suitable, but due to the toxicity of cadmium
it is a little harder to find. *Zinc-plated hardware offers minimal
protection because the zinc coating is so thin. *If the hardware is
used in an application where minimal strength is needed, consider
aluminum hardware itself.

There are many joint compounds on the market for joining aluminum to
aluminum. *Noalox and Penetrox are two common brands. *These
compounds are typically a petroleum grease containing zinc particles.
These particles are usually produced by spraying molten zinc and air
through a nozzle. *This produces small, irregular particles whose sharp
edges pierce the aluminum oxide surface film when the aluminum
pieces are tightly clamped together. *This produces a good
electrical contact, and the zinc is very compatible with the
aluminum from a corrosion standpoint.

Whatever you do, avoid any contact of copper with the aluminum.
Where the transmission line connects, be sure and heavily coat any
copper solder lugs with solder. *Try to keep a hot-dipped galvanized
washer between the lug and the aluminum.

Send me an email and I can send you some good articles on corrosion
that you might find interesting and informative. *My experience
comes from many years working in the chemical industry. *Even so, I
found the plant metallurgist to be a vital resource in material
selection for the instrumentation I designed.

--
73, Dr. Barry L. Ornitz *WA4VZQ
- Hide quoted text -

- Show quoted text -

Ive used anti-sieze compounds, they also are basicaly zinc and grease
and often more economical than the Noalox and Penatrox brands.
I have two of the mentioned antennas,one was given to me and the other
I bought at a hamfest. Apparently the weak link in these is the traps,
now I have two antennas that I cant get to work. The next time I move
which will probably be soon I may have a place where I can at least
use them for parts.


Jimmie

Jim Lux wrote:
lagagnon wrote:
I am about to refurbish an old Hy-Gain TH3-Mk3 Thunderbird tri-band
yagi. This yagi has been used in a coastal environment and thus the
aluminum is slightly pitted and most of the connecting hardware needs
replacing.

I figure steel wool would work fine for the aluminum tubing,

Avoid steel wool. Inevitably, it will leave little iron/steel fibers
behind, which will rust/corrode/react with the aluminum.

Hi Jim,

I keep hearing about steel wool rusting in/corroding Aluminum, but does
anyone have actual evidence? I've been looking on the web, and although
apparently using steel wool on AL will cause warts, bad breath, and the
downfall of the free world, all I've found is admonitions not to use it.
Maybe I'll try an experiment - I have some old antenna tubing.

There's just something a little strange about this. For the steel
particles to corrode the AL, they would have to detach, (easy enough)
settle into pores in the Aluminum at sizes small enough to do that,
(hmmm, those are pretty tiny steel particles) or have some odd property
of sticking to the AL despite cleaning. Then I guess it's a race between
rust and galvanic corrosion?


Use synthetic scrubbies (3M ScotchBrite) instead.

Bronze or stainless steel wool might be a good material to use. Boaters
use it on aluminum.

- 73 de Mike N3LI -

On Apr 29, 10:37*am, Michael Coslo wrote:
Jim Lux wrote:
lagagnon wrote:
I am about to refurbish an old Hy-Gain TH3-Mk3 Thunderbird tri-band
yagi. This yagi has been used in a coastal environment and thus the
aluminum is slightly pitted and most of the connecting hardware needs
replacing.

I figure steel wool would work fine for the aluminum tubing,

Avoid steel wool. Inevitably, it will leave little iron/steel fibers
behind, which will rust/corrode/react with the aluminum.

* * * * Hi Jim,

I keep hearing about steel wool rusting in/corroding Aluminum, but does
anyone have actual evidence? I've been looking on the web, and although
apparently using steel wool on AL will cause warts, bad breath, and the
downfall of the free world, all I've found is admonitions not to use it.
Maybe I'll try an experiment - I have some old antenna tubing.

There's just something a little strange about this. For the steel
particles to corrode the AL, they would have to detach, (easy enough)
settle into pores in the Aluminum at sizes small enough to do that,
(hmmm, those are pretty tiny steel particles) or have some odd property
of sticking to the AL despite cleaning. Then I guess it's a race between
rust and galvanic corrosion?

Use synthetic scrubbies (3M ScotchBrite) instead.

Bronze or stainless steel wool might be a good material to use. Boaters
use it on aluminum.

* * * * - 73 de Mike N3LI -

When you scour with the steel wool it will cut into the soft Al and
break off. You wont know about it until it starts to rust. Some
aluminum alloys dont seem to have as much of a problem with this but
others do. Ive had it happen to me, warned someone who still tried it
and had no problem.

Jimmie

Michael Coslo wrote:
Jim Lux wrote:
lagagnon wrote:
I am about to refurbish an old Hy-Gain TH3-Mk3 Thunderbird tri-band
yagi. This yagi has been used in a coastal environment and thus the
aluminum is slightly pitted and most of the connecting hardware needs
replacing.

I figure steel wool would work fine for the aluminum tubing,

Avoid steel wool. Inevitably, it will leave little iron/steel fibers
behind, which will rust/corrode/react with the aluminum.

Hi Jim,

I keep hearing about steel wool rusting in/corroding Aluminum, but does
anyone have actual evidence? I've been looking on the web, and although
apparently using steel wool on AL will cause warts, bad breath, and the
downfall of the free world, all I've found is admonitions not to use it.
Maybe I'll try an experiment - I have some old antenna tubing.

Go for it.

There's just something a little strange about this. For the steel
particles to corrode the AL, they would have to detach, (easy enough)
settle into pores in the Aluminum at sizes small enough to do that,
(hmmm, those are pretty tiny steel particles) or have some odd property
of sticking to the AL despite cleaning.

steel is much harder than aluminum, so the little fibers jam into the
relatively soft aluminum and make their own holes.


Then I guess it's a race between
rust and galvanic corrosion?

Yep..



Use synthetic scrubbies (3M ScotchBrite) instead.

Bronze or stainless steel wool might be a good material to use. Boaters
use it on aluminum.

- 73 de Mike N3LI -



The other thing to keep in mind with this sort of thing is the expected
life. Hey, if it's only going to be up for a year or two or three, it
probably doesn't matter. If you're going to expect your grandchildren's
children to use it unchanged, a bit more care might be required.

dave wrote in
:

Bruce wrote:
(Dave Platt) wrote in
:

I figure steel wool would work fine for the aluminum tubing,
I've read that it is *not* a good idea to use steel wool to clean up
aluminum, especially if it's going to be exposed to the weather.
There's a tendency for tiny bits of the steel to get caught in the
aluminum... it'll rust.

I'd suggest using a 3M (or generic equivalent) green abrasive
scrubbing pad. These pads are rough enough to remove oxidation from
copper PC board material, so I imagine they'll shine up aluminum
just as well, but they won't leave rustable material behind.

Neverdull is far better to use.

http://www.nevrdull.com/



Isn't the oxide good? Doesn't it protect the metal?


Yes, but it is non-conductive.

I keep hearing about steel wool rusting in/corroding Aluminum, but does
anyone have actual evidence?


Yeah, the mast on my sailboat as done by a previous owner of the boat.
It has some serious cosmetic corrosion and small pitting (but didn't
effect the mast's functionality) where the PO used steel wool to
remove some boat adhesive he accidently got on the mast. There were
small pits in that area. This is not as serious as aluminun to
stainless steel hardware bimetalic corrosion. SOP for a boat mast is
to used threaded bolts, not self tapping screws and to tap the hole.
Then we put in some version of Loctite (don't remember which one there
are many varieties of Loctite) designed for the purpose and sold at
boating stores among many other places. That minimized the bimetalic
corrosion effect. I never had any problems with the masts on my
sailboat after I enlarged the corroded holes a size larger and then
tapped them and put the SS machine screws in. Using anything other
than 316 SS screws is inviting disaster on a boat. Hardware starts to
fall off boats.

BTW my small sailboat sank last year, but that had nothing to do with
corrosion. My larger boat was donated to the Sea Scouts and I'm out
of sailing now. Wife (and crew) has had arthritis and had a triple
bypass a years ago. I just can't send her up the mast anymore :-).

Jon W3JT

The problem with stainless steel wool is that the consumer has little
control over what it actually is. There are many grades of stainless
and some grades do rust (as I found out when some got into my non-skid
on my boat.) It not as bad as ordinary steel wool, but it was a
problem, particularly when I bought it specifically to avoid rust on
my boat(s). I suspect SS wool is not marine grade such as 316 and
304, the two most common types on boats...they have different
purposes, but I forget what the differences and uses are for each one.

I haven't had a problem with bronze wool on a boat, but I think I'll
stick to emery or scotch brite for my antenna...the 2nd next to do on
my list.

Jon W3JT


On Wed, 29 Apr 2009 10:37:21 -0400, Michael Coslo
wrote:

Jim Lux wrote:
lagagnon wrote:
I am about to refurbish an old Hy-Gain TH3-Mk3 Thunderbird tri-band
yagi. This yagi has been used in a coastal environment and thus the
aluminum is slightly pitted and most of the connecting hardware needs
replacing.

I figure steel wool would work fine for the aluminum tubing,

Avoid steel wool. Inevitably, it will leave little iron/steel fibers
behind, which will rust/corrode/react with the aluminum.

Hi Jim,

I keep hearing about steel wool rusting in/corroding Aluminum, but does
anyone have actual evidence? I've been looking on the web, and although
apparently using steel wool on AL will cause warts, bad breath, and the
downfall of the free world, all I've found is admonitions not to use it.
Maybe I'll try an experiment - I have some old antenna tubing.

There's just something a little strange about this. For the steel
particles to corrode the AL, they would have to detach, (easy enough)
settle into pores in the Aluminum at sizes small enough to do that,
(hmmm, those are pretty tiny steel particles) or have some odd property
of sticking to the AL despite cleaning. Then I guess it's a race between
rust and galvanic corrosion?


Use synthetic scrubbies (3M ScotchBrite) instead.

Bronze or stainless steel wool might be a good material to use. Boaters
use it on aluminum.

- 73 de Mike N3LI -