The AM Forum

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???

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

I have used 'wire wheel and spoke' cleaner available at most automotive stores. Works on silver also.

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

good luck!

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

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.

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.

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.

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.

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...

Thanks to All!!!  
A great bunch of guys here!

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.

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!

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

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........

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.

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

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

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

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.

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.

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.

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.

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

--->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

So is sugar and baking soda in heavy concentrations

And beer for the op.

  There are gold irridite after treatments for cadmium plating that give the plated steel chassis a golden sheen, resembling the nicotine preservative often given by self sacrificing amateurs. While true cad plating is done far less nowdays over environmental issues the golden irridite is still availble . Many of the new bolts used in auotomotive applications are now gold irridite finished . (AKA Zinc Dihromate)

  BTW: "Alodine" is a trademark for an iridite conversion product. It is supplied by other makers as well.

Bringing this back to the top after a long sleep.

My SX-73/R274 has some sort of finish with a pale yellow tint on the chassis, it looks as new.

Henry Radio uses a dark alodine, I think, on almost all their ham and commercial amps. 

Carl

Alodine is sealant for aluminum and NOT a cleaner. The product that will do the job without fail is called Alumiprep 33. This will take an aluminum surface down to a pure state, which can then be painted, anodized or alodined.

One source is here:

http://www.aircraftspruce.com/catalog/cspages/alumiprep.php (http://www.aircraftspruce.com/catalog/cspages/alumiprep.php)

This same site sells Alodine as well. Alodine is a surface preparation that stabilizes the aluminum and prevents surface oxidation from occurring at all. Alodine 1201 formula gives the yellow finish most people think is cadmium (Most times it isn't cadmium on Ham gear; an urban myth. And if cadmium is used it's only on steel chassis. Mil spec gear is a different thing where MFP varnish is often used, or anodizing like on the R390a chassis parts.) Also, Alodine 1101 formula is a clear version. Alodine should be applied immediately after rinsing off the Alumiprep, before the aluminum oxidizes.

Now this stuff is mixed into a solution, liberally applied to the surface and then rinsed with water. It will remove all the corrosion and the aluminum will look as new.

Here's a photo of a chassis for an 75A-2a that received this treatment that is currently being restored and finished up in my shop. I never use an abrasive since none of these chassis had the "brushed aluminum" look which you will always get using a Scotchbrite pad. Once done it can never be removed. To me using a pad just makes it look like a scratched up chassis. This metal prep will make it look like the original finish with very little effort. Here's the image.

(http://www.vikingvintage.com/col75a2ar2.jpg)

Here's another image which shows how perfect the surface comes out on all the aluminum parts. This image shows a natural aluminum with no Alodine used, many days after the cleaning process was done. (BTW ... How do you like my Collins spec lacing on the new harness?)

(http://www.vikingvintage.com/col75a2ar1.jpg)

BTW ... If used in solution, it will not remove silk screening on the chassis. Also if you look at the aluminum IF/RF transformer covers the lettering is intact. These also received the same treatments and look as if new with all the lettering. Alumiprep is designed to only chemically react with aluminum & aluminum oxide, as well as other oxides to a lesser degree. This chemical is somewhat acidic and you should use gloves and eye protection when using it.

I have not found a better way to bring back the original finish on aluminum chassis than this product. When both products are used, this preps aluminum for painting extremely well. I use this on R-390a front panels, after chemically stripping the old paint and before applying the chromate primer. No scrubbing or rubbing is really required with this stuff. In fact a gentle hand is preferred since the process is occurring at the molecular level. Hard rubbing will scratch the surface and actually slow down the process. I use a soft natural hair paint brush with the Alumiprep and rub liberal amounts of the solution around gingerly and then rinse & repeat until all the marks and oxidation is gone. Don't let the stuff sit in place, keep moving the stuff around on the piece. Same with the Alodine.

Scratches get hidden well since they are totally cleaned as well and sort of disappear.

BTW, since this product removes all the oxides and leaves a pure aluminum surface, it is interesting to watch the aluminum surface form a surface coating of oxides which it will do in a very short amount of time. Aluminum oxidizes very quickly, but once that surface coat forms it slows. It is because of this it is important to dry the surface quickly after rinsing with water if you chose not to use Alodine and leave the pure aluminum. It spots up easy due to the higher oxygen content in water droplets and the aluminum oxidizes at a different rate under the drops leaving spots.

Ok ... I just gave away one of my trade secrets!!

John
W2WDX

Did you completely disassemble that thing before you gave it the treatment, or do it with the components etc on?

Looks stunning - and I like the lacing job on the hah-ness!

Well in this case the components were removed and the chassis disassembled. I restore and resell, so my methods are a bit more sophisticated to save time and be repeatable. I actually put the components in a plastic tub with a large batch of solution. I keep the solution agitated with an all plastic & stainless fish tank aquarium submersible pump. An agitated acid bath so to speak. I keep this next to a plastic shop sink so I can remove the pieces from the bath and rinse under running water rubbing with a large soft horsehair paint brush. Ventilation is a good idea, unless you enjoy the acrid smell of acids at work. I ventilate but still use a respirator, gloves and eye protection.

However, with care and a spray bottle of water you can spot clean without removing most components.

I put some of the Alumiprep on a small wetted paintbrush and treat the specific area until the corrosion is gone. Then I saturate the area with water from the spray bottle. Care must be taken not to get any of the Alumiprep into things like transformers and I plug up any holes in the chassis with an assortment of little rubber plugs I have collected. I usually back out tube sockets and plug the holes for both the sockets and the mounting screws with these stoppers. Large transformers and chokes I will lift up from the chassis as much as I can and clean the chassis with care to avoid the xfomers.

Oddly, the ceramic trimmer caps like the Erie type used on the Collins 75a series seem to like being treated with this stuff IF heavily rinsed with water. Same thing with rotary switches. Soak in the solution briefly, rub them with the brush, work them mechanically, and rinse the snot out of them. Dry them carefully with a hair dryer (don't get them hot, just warmed slightly) and walla, perfectly restored and working trimmer caps and switches! Bonus!

You can also apply the stuff straight on a paper towel and spot clean, then wipe down with water on another paper towel and another and another. USE GLOVES. If you don't your hands will peel, like you had sunburn, in a few days! :-)

Another good idea is to get some litmus paper. You can check the acidity of the water rinse to see if the acids are diluted enough to stop rinsing.

If you do not remove components and do the brush and rinse method, of course make sure everything dries completely for a few days before you start applying power to anything.

John
W2WDX