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Author Topic: How to Get Rid of Corrosion on Aluminum Chassis  (Read 85011 times)
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Ed/KB1HYS
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« on: March 08, 2005, 04:34:54 PM »

I have a problem with one specific area on a chassis in my Valiant, I have tried everything I could think of to get rid of and stop the corrosion from progressing.  The area in question looks like it had some Coke (pepsi?) spilt on it at one time, I had to clean off a lot of  sticky brown goo from the cabinet and the rest of the rig. I have cleaned the area and treated it with a couple different things. Including one Very expensive anti-corrosion treatment that I got at the local airport.  The corrosion always seems to come back, the area is pitted but not yet unservicable.  I'd like to save it before I need to replace the chassis.
  So any suggestions???
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
W2PFY
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« Reply #1 on: March 08, 2005, 05:38:18 PM »

go out and get a can of chrome cleaner. It says clearly on the can not to use it on Aluminum. Try it on a piece of test aluminum first. It worked for me but use it with care and netraulize it with water on a rag after you have cleaned up an area.  Please don't sue me if it doesn't work because I have no money :lol:

Let me know how you make out.

Terry
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k3zrf
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« Reply #2 on: March 08, 2005, 08:07:42 PM »

I have used 'wire wheel and spoke' cleaner available at most automotive stores. Works on silver also.
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dave/zrf
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xe1yzy
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« Reply #3 on: March 08, 2005, 09:37:15 PM »

Im use gojo hands clenear WITH pumice, ( the orange one) is excellent and work great!

good luck!
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w3jn
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« Reply #4 on: March 09, 2005, 08:36:53 AM »

Are you sure the corrosion is progressing?  Aluminum *instantly* oxidizes in the presence of air to provide a tough coating of aluminum oxide which is fairly impervious to other materials.  This thin coating is what keeps unpainted aluminum from decaying into dust.  

If it is indeed still progressing, there might be some acid that continues to eat away at the metal.  Or there might be some galvanic reaction from a nearby component and/or current flowing thru the chassis.

Curious.

73 John
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N8ECR
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« Reply #5 on: March 09, 2005, 01:45:07 PM »

I had this same thing happen on some of my stuff.  My shack was in the basement , and right under a dish washer, this thing had a sudden failer and discharged , ruining every thing below in the shacka signal shifter, and a globe King 400 got the worst of it.  Even after 20 years, a rack panel that laid in this discharge was sanded and litely primed and put in a rack cabinet, only to later start oozing out brown yuk... :shock:  and 20 years later mind you.


You might concider soaking it in water and baking soda

As for my panel I thru it out, and it spoiled the rack I installed it in.
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W1RKW
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« Reply #6 on: March 09, 2005, 03:26:09 PM »

Yes, try neutralizing with a baking soda solution then dry it off then immediately and lightly coat the area with an oily substance like vaseline or a light machine oil to create an air barrier.  The oil probably will attract dust over time but it should help control if not stop the oxidation.
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Bob
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K1MVP
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« Reply #7 on: March 09, 2005, 06:50:24 PM »

Hi Ed,
 You mentioned the corrosion is in on specific area on your xmtr.
 There is one method I have used in restoring a while back,a badly
 rusted and corroded SX71 receiver.
 I found I had to resort to SANDBLAST the receiver, including part
 of the chassis.--It did work, but I had to be very careful in masking
 off the chassis which can be time consuming BUT I did get rid of
 the corrosion, and then primed the effected area with a real quality
 self etching automotive primer.(not the "cheap" stuff)
 It did work for me, as I was able to "save" the chassis and not have
 to "scrap" the receiver.(I would only recomend it for areas that are
 "localized" --to do the whole chassis would require dissasembly, and
 that IMO would be LOTS of work and time.
 Hope this helps, you out with another approach(a bit "drastic) but it
 might work.
                                        73, Rene, K1MVP

 P.S., I have an article on the "71" restoration on East Coast Sound
         here on the am website, which will show you more details.
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Jim, W5JO
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« Reply #8 on: March 09, 2005, 06:57:27 PM »

Aircraft people will use a 25% or so vinegar solution of distilled water and a 3M pad to remove it on flat surfaces, or if it requires, a soft bristled bursh (read very soft bristled that will not scratch the surface).  Remember the inner core of aluminum is pure and the surfaces are coated with different elements to prevent the aluminum from oxidizing.  

Once cleaned and flushed with distilled water, coat the surface with LPS 3.  It is a very thick jelly like substance and if used on capacitor plates, needs to be applied in a very smooth layer to prevent variation in the capitance.  On a chassis, it won't matter.  

Do not use steel wool or a steel bristled brush to clean it.  If you scratch the surface of the aluminum you can create places for oxygen to enter and set up real problems.
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ve6pg
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« Reply #9 on: March 09, 2005, 08:01:07 PM »

I WORK IN AVIATION...ALL THAT HAS BEEN MENTIONED IS GOOD,BUT HERE IS WHAT I WOULD DO. CLEAN THE AREA WITH ALCOHOL,BASICALLY DE-GREASING THE AREA..NEXT USE A MAROON COLOURED SCOTCH BRITE PAD...USE THE PAD IN ONE DIRECTION,NOT CIRCULAR...BACK AND FORTH IN A NORTH-SOUTH DIRECTION.THE AREA YOU ARE WORKING ON WITH TURN A DARK COLOUR,WIPE WITH A CLEAN RAG.NEXT POUR SOME DISTILLED WATER ON THE AREA,AND USE THE SCOTCH BRITE PAD AGAIN..WIPE CLEAN,AND WIPE IT DOWN WITH DISTILLED WATER....NOW,DO A WATER-BREAK TEST..POUR SOME DISTILLED WATER ON THE AREA...IT SHOULD JUST SIT THERE,IF YOU HAVE REMOVED ALL THE JUNK,OILS,ETC..WHEN YOU REACH THIS POINT,YOU APPLY SOME ALODINE TO THE REPAIR AREA.ALODINE IS TO PROTECT THE METAL FROM ANY FURTHER CORROSION.IT CAN COME AS A POWDER,BUT USUALLY IT IS A LIQUID..IT IS APPLIED AS A LIQUID...PUT SOME ON A RAG,AND WIPE THE REPAIR AREA..DONT LET IT SIT WET ON THE AREA TOO LONG..THE LONGER IT SITS,THE DARKER YOUR REPAIR AREA WILL GET..SO...THIS SHOULD STOP ANY OF THE CORROSION FROM COMING BACK...AS FAR AS YOU GETTING SOME ALODINE,GO TO YOUR LOCAL AIRCRAFT SHEET METAL SHOP,AND ASK ONE OF THE MECHANICS FOR A COUPLE OF OUNCES OF ALODINE...MAKE SURE IT IS FRESH,AS IT LOSES IT STRENGTH OVER TIME,AND IF IT IS STORED IN A BATH TYPE CONTAINER,CONTAMINATION FROM PREVIOUS METAL WORK WILL BE PRESENT,AND THE COLOUR WILL BE A DARK BROWN...FRESH ALODINE IS LIKE WATER,BUT HAS A SLIGHT YELLOW-GREEN COLOUR...I HOPE THIS LONG DIATRIBE HELPS,IT REALLY DOESNT TAKE THAT LONG TO DO...P.S. ASK FOR ALODINE 1201....73...TIM...
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Ed/KB1HYS
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« Reply #10 on: March 09, 2005, 09:18:32 PM »

Thanks to All!!!  
A great bunch of guys here!
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
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« Reply #11 on: March 09, 2005, 10:06:51 PM »

One other thing that has worked for me is a product call CIP-100 made by Steris. It is a high pH product. I have used this with capacitors and they looked like they came right off of the show-room floor.
Gud Luck.
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
Bacon, WA3WDR
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« Reply #12 on: March 10, 2005, 12:51:03 AM »

This reminds me... there is aluminum, and there is coated aluminum.  The two coating types I know are "anodized" and "irridated"... if you scrape off such a coating, it looks OK for a while, but then it oxidizes and gets gray.  And it picks up fingerprints like crazy!  I think the "clear" irridite is nice, but it is not as strong as an anodized coating.  But anodization leaves an insulating layer that is hard to break through!  In fact, it is so hard that I think it is rough on drill bits.  Not the thing for a chassis that is supposed to provide an easy ground.  But you can grab it and touch it all day long, and your fingers will not leave those dark marks that show up later.

I don't know if an irridite coating can be patched onto a chassis, and I don't know what kind of coating was typically provided, but I'll guarantee that some kind of coating is common.  If I sand aluminum, it's always the same... don't touch it, or you leave dark fingerprints!

<edit> I just saw Jim's post above.   LPS 3...  Hmmm, I learn something new every day!
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w3jn
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« Reply #13 on: March 10, 2005, 06:58:42 AM »

Few "hammy hambone" radios used anodized aluminum chassis.   THe only one that I can think of is the TMC GPR-90, which was a high-end semi-professional receiver, and possibly the Collins S-line.  It is somewhat common in military equipment.

Most radios used zinc-plated steel chassis.  The chassis would collect dust over the years, and the dust would absorb humidity and corrode the plating.  You end up with a chassis that looks like it has acne.  If the ham who owned the radio was a heavy smoker, the nicotine coating acts as a great preservative (of the radio, not necessarily the ham's lungs).  Use Westley's whitewall cleaner to instantly dissolve the nicotine.

73 John
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KL7OF
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« Reply #14 on: March 10, 2005, 11:10:48 AM »

Nicotine seems to be a great preserver.....I bought some radios in an estate sale that were literally coated inside and out from years of heavy smoking....They looked like hell when I brought them home....I used alcohol and the orange cleaner in the spray bottle to clean and clean and clean and there were very nicely preserved radios under all that goo.....go figure.....The ham that owned the radios died of old age........
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WA1GFZ
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« Reply #15 on: March 10, 2005, 11:24:02 AM »

John,
Airplane builders loved smokers. The smoke would seal small air leaks
around rivits etc. I'm sure they were sorry to see no smoking signs added
in commerical aircraft.
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w3jn
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« Reply #16 on: March 10, 2005, 01:12:21 PM »

Mark - I'm unaware of any radio that has a gold-tinted plating EXCEPT for anodized aluminum chassis such as military and TMC radios.  Perhaps later Hallicrafters radios such as the SX-117, SR-150, etc. had anodized chassis as well - can't remember.  Never had a B&W rig so I can't comment there...  

As far as 40s-50s Hallicrafters radios go, I've NEVER seen one with gold tinted plating.  You may be mistaking this for nicotine schmeg or MFP treatment of some sort.  I have a couple of SX-73s with the typical brown-tinted MFP varnish on the chassis.  And I just finished up a '62 vintage SX-101A (the kind with knobs identical to a SX-117) and it has a straight zinc-plated steel chassis.

I would say that if it scrubs off with Westley's Bleche-White it is nicotine... you can't scrub off the coating on anodized aluminum.

73 John
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w3jn
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« Reply #17 on: March 10, 2005, 02:56:11 PM »

Mark - you're right!  Now that I think about it the metal shroud that covers the back of the dial and the variable cap cover ARE gold but the rest of the chassis on mine is just zinc-plated steel.

Looks FB but I can see what you mean about some of the gold having worn off....  haven;t a clue of how to avoid that.

BTW if you want better AM audio outta that thing clip the .047 uF capacitor that's in the ANL circuit (there's a 180K resistor from the detector, in series with a 1 meg resistor that goes to the ANL diode, with a .047 cap tied to the junction of the two resistors).  This cap causes flat-topping of the audio when it gets towards 80% modulation.  ANL operation is minimally affected, but the radio sounds a LOT cleaner when listening to stations with the East Coast Sound.

73 John
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w3jn
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« Reply #18 on: March 10, 2005, 03:17:48 PM »

Is yours magnetic?  If so it's probably zinc-plated steel with a thin golden electroplating of some sort (or maybe anodization).  If not, it's probably aluminum.

73 John
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« Reply #19 on: March 10, 2005, 05:09:06 PM »

Quote from: Bacon, WA3WDR
This reminds me... there is aluminum, and there is coated aluminum.  The two coating types I know are "anodized" and "irridated"... if you scrape off such a coating, it looks OK for a while, but then it oxidizes and gets gray.  And it picks up fingerprints like crazy!  I think the "clear" irridite is nice, but it is not as strong as an anodized coating.  But anodization leaves an insulating layer that is hard to break through!  In fact, it is so hard that I think it is rough on drill bits.  Not the thing for a chassis that is supposed to provide an easy ground.  But you can grab it and touch it all day long, and your fingers will not leave those dark marks that show up later.

I don't know if an irridite coating can be patched onto a chassis, and I don't know what kind of coating was typically provided, but I'll guarantee that some kind of coating is common.  If I sand aluminum, it's always the same... don't touch it, or you leave dark fingerprints!

<edit> I just saw Jim's post above.   LPS 3...  Hmmm, I learn something new every day!


I've made brushed aluminum front panels and what Bacon says is true.  But I've managed to come up with my own way of preventing fingerprints and the turning of gray of the surface.  I found that a spraying a rag with DeOxIt and polishing the surface with it prevents oxidation.  The metal feels clean too.  You can touch all you want.
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Bob
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Bacon, WA3WDR
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« Reply #20 on: March 10, 2005, 08:53:20 PM »

Gold is too expensive to blow it all over low-cost commercial gear like that.  I think it's cadmium or something.

Cadmium is a common coating for steel.  It has kind of a yellowish color and it keeps the steel from rusting.  My guess on that Hallicrafters gear is that it is some kind of cadmium coat.

Love that old Hallicrafters stuff.
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Jim, W5JO
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« Reply #21 on: March 10, 2005, 10:46:38 PM »

The B&W chassis is alodined which is the liquid the VE mentioned.  It is a seal coating to prevent corrison and is also used on powerplants in small aircraft which are cast from a mixture of aluminum and magnesium.  It prevents other corrosion for setting up on the surface.  Usually aluminum has the two processes of annodizing or alodining.   You all probably have seen the briefcases that has been annodized.

Either of these processes can be breached with improper storage such as dust that gathers then holds water or other liquids that will eventually cause problems if there is a break in the coating.  You will have those breaks where screw holes have been drilled or socket holes have been punched after the chassis has been processed.

 I have a B&W 5100B that was used most of it's life or stored in a house and the chassis and all aluminum surfaces are still coated and in good condition.  When cleaning an aluminum surface that has alodine on it, do not scratch it, for it will break the surface and water will ingress into the aluminum or other material to begin the corrison process.  Wash it with distilled water and a mild soap first.  If it has been scratched  then rub it with Scotch Brite pads then follow the direction for applying the alodine.  The process is not difficult just time consuming.  Be sure to dry it thoroughly after cleaning.

Aluminum sheets are referenced by a number that specifies the chemistry of the aluminum alloy.  It may contain some copper or other metal to give it flexibility and added strenth, since pure aluminum is very soft.  2024 T3 is an example.  The first number specifies the alloy mixed with the aluminum and the T3 specifies coat process by which another chemical is added to prevent corossion.  That is why aluminum chassis turn dark when the surface is scratched.

If you don't want to do the alodining process to cover places that have been cleaned, then prime it with some zinc primer, but remember that primer scratches easy.  it is about the only primer that will adhere to aluminum surfaces.  Some companies call it "self etching".

From the picture of the SX 101A, it is difficult to tell, but I am guessing it has been alodined.
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KE1GF
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« Reply #22 on: March 11, 2005, 02:37:39 AM »

Ed I don't know what's eating away at your chassis possibly some strong bass got knocked into the rig, take a squirt on her to neutralize the reaction.
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WA1GFZ
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« Reply #23 on: March 11, 2005, 08:15:46 AM »

I have a friend serious into battle bots. He has metal coated in various colors. I think he pays around $60 a basket of metal. I've had a chance to throw in parts to fill the basket but he usually picks weird colors like red
so never got involved. This process would be good if one was rebuilding from a bare chassis up.  fc
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WBear2GCR
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« Reply #24 on: June 12, 2005, 09:59:55 AM »

--->ALODINE IS DANGEROUS STUFF!! <---[/color]

Wear gloves and be sure you work in a well ventilated area.
Notwithstanding what any aircraft mechnaics may or may not do.

Alodine is a passive (chemical, no electricity) chromating system. Usually a two part system.

The aluminum chassis that are gold colored are usually chromated. You can do a "golden" colored anodize - which you see on some front panels in audio gear etc. - but this is rare in electronics/radio gear. The anodize usually looks like there is a thin "clear coat" over the color, whereas the chromate is always matte and dull, also relatively soft compared to anodize.

Judicious application of "oven cleaner" in the form of LYE solution followed by water rinses and then some mild acid (vinegar or lemon juice) followed by baking soda and then water will remove almost anything from aluminim. Some moderate abrasion with a scotchbrite pad in there won't hurt in some cases.

WEAR GLOVES AND EYEPROTECTION WHEN WORKING WITH LYE/OVEN CLEANERs or ACIDS!! <---

The suitability of this depends on where ur working on a piece of course.

Baking soda as a powder with a little water also seems to do a nice job of cleaning rather ratty looking raw aluminium and won't hurt anything. Worth giving it a shot too... not sure what the process is that is doing the work here.

      _-_-bear
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