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Restoring a Hy-Gain Yagi...
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 |
Restoring a Hy-Gain Yagi...
Larry,
I use "Ox-Gard", available from the local "Do-It Center" hardware store outlet. Preserves overlap joints on aluminum tubing and makes them easy to adjust and disassemble after years outdoors. Works fine for radio waves, but does not conduct DC. Found this out the hard way in an application where I was passing RF alongside some DC signaling information. The RF got through just fine, the DC not so much. -larry K8UT "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 |
Restoring a Hy-Gain Yagi...
On Apr 28, 3:43*pm, 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, 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 I would stay away from the steel wool. Bits of it will imbed in the Al and rust. Jimmie |
Restoring a Hy-Gain Yagi...
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. Use synthetic scrubbies (3M ScotchBrite) instead. 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 |
Restoring a Hy-Gain Yagi...
On Tue, 28 Apr 2009 12:43:59 -0700 (PDT), 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, 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 I just called Bencher/Butternut about my aluminun vertical and they suggested NOT using steel wool for cleaning because the residue of the steel wool rusts very easily. I know this is true from my boat where we generally use bronze wool to avoid rust. The steel wool sheds (and I know this from hard experience) as a bear to clean out of stuff, such as the deck of my boat. The Butternut guy suggest that rather than steel wool use either emery paper or a Scotchbright pad as they do not leave residue. Butternut also has a conductive grease that they provide with their antennas to keep the metal to metal joints conductive. Steel wool residue can also cause bimetalic corrosion with aluminum. Most assuredly use stainless steel fitting and screws. Ordinary screws/nuts will rust very rabidly. Any boat owner knows that many so-called compression clamps, allegedly in stainless, do not have stainless bolts to tighten them. Most of us take a magnet to the boating store to ensure we got the right things. BTW a boating store is generally a pretty good place to get stainless steel hardware. They know that a boat owner will scream bloody murder and besmirch their reputation if they sell anything but the top quality stuff. We ran one boating store out of town for selling shoddy stuff. I'm embarking on exactly the same rebuild on my Butternut vertical so I just talked to the factory specialist on this very subject just last week. My spare parts just arrived yesterday. I'm rebuilding because after 25 years, the wind flexed the tube that mount the antenna, a vertical, into the ground. I guess that is not too bad service for this antenna. Jon Teske, W3JT Maryland |
Restoring a Hy-Gain Yagi...
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Restoring a Hy-Gain Yagi...
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. I know how to test the traps, but I am wondering whether to use stainless steel or galvanized hardware? I believe that you can get some amount of electrolysis if galvanized metal and aluminum are in contact, especially if the aluminum is not well-anodized or if there is electrolyte around (e.g. if your area is subject to salt spray). Some people in the boating trade claim "no problem", others state that you should never use zinc-galvanized and aluminum together. Stainless-steel-and-aluminum seems to be the preferred combination. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Restoring a Hy-Gain Yagi...
Owen Duffy wrote in
: JIMMIE wrote in news:9b6a811c-4f7a-4686-a503- : ... 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 .... Apologies, I mis-quoted there, the text was by lagagnon . Owen |
Restoring a Hy-Gain Yagi...
Dave Platt wrote:
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. 3M pads and Bon Ami cleaner works well. And clean aluminum has better gain. One of my 432 antennas tested at Central States gained .4dB between very dirty oxidized elements and cleaned elements. tom K0TAR |
Restoring a Hy-Gain Yagi...
"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 |
Restoring a Hy-Gain Yagi...
"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 |
Restoring a Hy-Gain Yagi...
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? |
Restoring a Hy-Gain Yagi...
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 |
Restoring a Hy-Gain Yagi...
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 - |
Restoring a Hy-Gain Yagi...
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 |
Restoring a Hy-Gain Yagi...
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. |
Restoring a Hy-Gain Yagi...
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. |
Restoring a Hy-Gain Yagi...
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 |
Restoring a Hy-Gain Yagi...
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 - |
Restoring a Hy-Gain Yagi...
"Michael Coslo" wrote in message
... Then I guess it's a race between rust and galvanic corrosion? The aluminum will prevent the steel from rusting at the expense of its own corrosion. Use synthetic scrubbies (3M ScotchBrite) instead. Bronze or stainless steel wool might be a good material to use. Boaters use it on aluminum. Because boaters do not understand corrosion and electrochemical reactions, they often choose poor materials. Brass is more cathodic than steel, the 400 grade ferritic and martensitic stainless steels are more cathodic than brass, the 300 grade austenitic stainless steels are more cathodic than the 400 grades, and precipitation hardenable stainless steels like 17-4PH lie between 300 and 400 grade stainless in being cathodic. The more anodic a material is, the faster it corrodes. The more cathodic (or noble) a metal is, the slower it corrodes. As I said earlier, I have several good, introductory articles on corrosion and galvanic series that I can send upon request by email. -- 73, Dr. Barry L. Ornitz WA4VZQ |
Restoring a Hy-Gain Yagi...
On Thu, 30 Apr 2009 00:41:21 -0400, "Dr. Barry L. Ornitz"
wrote: "Michael Coslo" wrote in message ... Then I guess it's a race between rust and galvanic corrosion? The aluminum will prevent the steel from rusting at the expense of its own corrosion. Use synthetic scrubbies (3M ScotchBrite) instead. Bronze or stainless steel wool might be a good material to use. Boaters use it on aluminum. Because boaters do not understand corrosion and electrochemical reactions, they often choose poor materials. Brass is more cathodic than steel, the 400 grade ferritic and martensitic stainless steels are more cathodic than brass, the 300 grade austenitic stainless steels are more cathodic than the 400 grades, and precipitation hardenable stainless steels like 17-4PH lie between 300 and 400 grade stainless in being cathodic. The more anodic a material is, the faster it corrodes. The more cathodic (or noble) a metal is, the slower it corrodes. As I said earlier, I have several good, introductory articles on corrosion and galvanic series that I can send upon request by email. As I discovered when I did a restoration and rebuild on my sailboat about 10 years ago. All of the original interior woodwork fittings on the boat were held in place by decorative brass screws. As the boat was built in 1971, but the time I got to it in the late 90's all the brass screws had "zincified" (probably not the correct term to a metallurgist, but one that appears in boating literature). This results in the screws having a pinkish color and they become very brittle. Any attempt at removing them resulted in the head breaking off or the Philips cross slot stripping out. I had to remove all of these with a screw removal tool. They were all replaced with coated SS screws, the coating for decorative purposes. At least among sailboaters, who for some reason appear to be more technically savvy than power boaters, galvanic corrosion is pretty well understood at least at a layman's level. Most boat repair books mention this and include the galvanic series and the relative "nobility" of various metals and alloys. Those of us who sail in salt water are also well aware of the need to put sacrificial zincs on our boats to prevent damage to other metal parts. Replacing these is a regular part of our annual maintenance. A very high percentage of sailboaters are also hams, far beyond our normal density in the overall population. Jon W3JT |
Restoring a Hy-Gain Yagi...
Dr. Barry L. Ornitz wrote:
"Michael Coslo" wrote in message ... Then I guess it's a race between rust and galvanic corrosion? The aluminum will prevent the steel from rusting at the expense of its own corrosion. Use synthetic scrubbies (3M ScotchBrite) instead. Bronze or stainless steel wool might be a good material to use. Boaters use it on aluminum. Because boaters do not understand corrosion and electrochemical reactions, they often choose poor materials. Brass is more cathodic than steel, the 400 grade ferritic and martensitic stainless steels are more cathodic than brass, the 300 grade austenitic stainless steels are more cathodic than the 400 grades, and precipitation hardenable stainless steels like 17-4PH lie between 300 and 400 grade stainless in being cathodic. The more anodic a material is, the faster it corrodes. The more cathodic (or noble) a metal is, the slower it corrodes. As I said earlier, I have several good, introductory articles on corrosion and galvanic series that I can send upon request by email. I'd be interested. I'm one of those folks who post an actual address in the newsgroup, so if you would be so kind. Thanks in advance... - 73 de Mike N3LI - |
Restoring a Hy-Gain Yagi...
"lagagnon" wrote in message ... .... 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? Larry VE7EA Penetrox P8a from Burndy (Framatome) Sells in 8.5 Oz. squeeze bottels. Last for years in a ham's toolbox. |
Larry VE7EA[/quote]
here is where to get the grease AMAZON.COM (( GB OX GARD )) and if you have the vintage Cushcraft A3.i can send you a printable email for this antenna IF YOU HAVE THE MODEL WITH THE BN-86 BALUN OR NEED IT ORDER# 242 from MFJ.COM 73 N4VGY |
Quote:
and if you have the vintage Cushcraft A3.i can send you a printable email for this antenna IF YOU HAVE THE MODEL WITH THE BN-86 BALUN OR NEED IT ORDER# 242 from MFJ.COM 73 N4VGY[/quote] A old Hy Gain antenna should have been anodized, hence when you clean the corrosion off it, you also remove the anodize finish which will make it corrode even faster. I guess the key would be to use all stainless steel hardware and fastners when you first assemble it - that way the only thing you have to contend with is the aluminum - which should last forever - as long as you keep the bugs out of the tubing. I have a old TET antenna out in the garage that had carbon steel hardware and plastic insulators. The carbon steel rusted and corroded and split the plastic hardware and had to be cut apart to move it from it's previous location. The owner thought that someone would just walk over and carry it home with them. But with each element of the beam being about 36' long - it would have been impossible to haul on the roof of a truck and I had to bring it home 100 miles. When my tower gets set up, I will order all new stainless steel hardware - which will probably be worth more then the whole antenna when it was new! Probably the best thing to do with a old antenna is to donate it to the less fortunate and buy a new one! |
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