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How to Get Rid of Corrosion on Aluminum Chassis

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Author Topic: How to Get Rid of Corrosion on Aluminum Chassis  (Read 72629 times)
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Jim, W5JO

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« Reply #25 on: June 12, 2005, 11:34:59 AM »

Quote from: BEAR
--->ALODINE IS DANGEROUS STUFF!! <---[/color]bear

So is sugar and baking soda in heavy concentrations
Steve - WB3HUZ
« Reply #26 on: June 12, 2005, 03:08:14 PM »

And beer for the op.
« Reply #27 on: November 08, 2009, 12:59:57 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

  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.
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« Reply #28 on: June 07, 2010, 08:33:32 PM »

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. 

« Reply #29 on: September 11, 2011, 12:24:09 AM »

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:


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.

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?)

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!!

Johnny Novice

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« Reply #30 on: September 11, 2011, 03:49:27 AM »

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!

FCC:  "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
« Reply #31 on: September 11, 2011, 12:56:59 PM »

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.

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