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Author Topic: Chemical Dip Cleaning of Aluminum  (Read 26224 times)
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Todd, KA1KAQ
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« on: June 23, 2010, 12:23:51 AM »

It's been years, but an old timer once showed me how to clean things like aluminum tube shields, IF cans and similar by a chemical dip process. Pretty sure it was a type of acid, probably banned by the nervous ninnies by now. It worked great, far more natural looking than polishing with fine steel wool. It would basically strip the crud off the outside leaving the aluminum like new, which resulted in the aluminum oxidizing after being rinsed, which turned it back to that nice, dull finish.

Some of the pieces have mild freckling on the top caused by long term oxidation to the point of corrosion setting in. Nothing serious, but it's probably going to require some kind of mind grinding/polishing to smooth them out. The one thing I want to avoid is that 'pimped up' look of over-polished pieces in a mid-30s receiver.
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« Reply #1 on: June 23, 2010, 12:32:56 AM »

Just thinking out loud here, Todd, but you might check into what the anodizing folks are using to prep the Al before anodizing. I've never done any anodizing, but I was reading the other day about how essential it is to have the Al perfectly clean before starting the process. One guy told about picking up a cleaned piece without gloves and after pulling it out of the anodizing solution found a nicely anodized piece with a perfect fingerprint in it.

ldb
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Jim, W5JO
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« Reply #2 on: June 23, 2010, 05:44:04 AM »

Muratic acid, but be cautious and handle with care.
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WD5JKO
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« Reply #3 on: June 23, 2010, 06:59:43 AM »


The usual treatment of Al prior to anodization is to dip the Al in a container of water and lye (caustic soda). The reaction will remove the aluminum oxide quickly, and then start removing the Al. The reaction is exothermic, and produces hydrogen gas. Drano is a combination of lye and Al powder; get it wet and watch out!

Edit: using Drano and water might be a good source of lye since there should be plenty of lye left after the Al powder is gone. Any chemists out there that can weigh in?

Read the part under "Hazard Analysis":
http://www.newton.dep.anl.gov/askasci/chem00/chem00831.htm

Jim
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W1VD
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« Reply #4 on: June 23, 2010, 07:46:03 AM »

At a previous place of employment we had a strong lye bath for 'finishing' aluminum. Aluminum parts or entire chassis were left in the vat overnight. In the morning  the piece looked pretty ugly - dark and blotchy - until it was washed. The result is a very uniform light gray colored finish that seemed to be fairly corrosion resistant. A coat of clear Krylon provides an even more durable finish. I have some pieces that were finished 35 years ago and still look like the day they were completed.

Note: Pieces were occasionally left in the bath by mistake over the weekend. Come Monday morning the original .050 aluminum was reduced to little more than tin foil thickness.       
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The Slab Bacon
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« Reply #5 on: June 23, 2010, 08:02:49 AM »

there is some stuff you can buy at major auto parts stores called "aluminum jelly"
it is a kin to the stuff for steel called "naval jelly". It works pretty good, I use it on the engine cases of my bike once or twice a year.

Also, there is some stuff out now called "etching mag / aluminum wheel cleaner". You spray it on, let it sit for a few minutes and then rinse THOROUGHLY with clear water this suff works extreemly well on aluminum wheels.

I believe both are a phosphoric acid compound. (chemical reagent)


                                                        The Slab Bacon
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WA1GFZ
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« Reply #6 on: June 23, 2010, 08:38:26 AM »

We have a number of benches with copper ground planes as a work surface.
To avoid the MSDS chemical SS, we use vinegar. It works great and makes the area smell like a salad bar. It also works great on silver. I have not tried aluminum yet.
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KC4VWU
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« Reply #7 on: June 23, 2010, 09:33:03 AM »

Todd,
         Eagle One still makes the old school mag wheel cleaner. Remember back in the day cleaning those old ET aluminum slots? Well, so anyways, you can still get that same old stinky stuff that tingles the 'ol fingers. I wanted to clean the grubby air variables in the Bandmaster, and those Saturday night crusin' memories came back to mind. Most of the stuff they have at the auto parts stores these days are for coated wheels; the spray and rinse wimpy stuff. But get the stuff in the silver spray bottle and it will clean the heck out of oxidized aluminum. For larger parts, you may need to buy a couple bottles and a plastic dish pan. 4-5 bucks a bottle.

Phil
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W2PFY
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« Reply #8 on: June 23, 2010, 10:36:26 AM »

I can't remember what I used but what I did was look at all the spray chemicals that were used for various purposes at an auto parts store. I looked for the one can that had the strongest label about being careful not to use it near or on aluminum and that was the cleaner I purchased. It worked, whatever it was??

I think a lot of wheels were aluminum and perhaps still are. Maybe that's what the manufacture was worried about?   
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Ed/KB1HYS
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« Reply #9 on: June 23, 2010, 10:59:14 AM »

almost any mild acid wash followed by a very throrough rinse should work.

For light work, a trip through the dishwasher is pretty good too.
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73 de Ed/KB1HYS
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« Reply #10 on: June 23, 2010, 11:01:24 AM »

Hi Todd,
Sounds like your working on those Comet Pro shields!
A few years back, old buzzard Bert (OBB), WA3JYU was cleaning some large air variables and I believe he used Westley's "Blech White" and it really cleaned up the aluminum to look like new.  The intended use is as a Tire cleaner and really works well on whitewalls and raised white letter tires.  It tells you to keep it away from Aluminum, so that is just what you want...
Joe, W3GMS      
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« Reply #11 on: June 23, 2010, 11:04:59 AM »

Anyone for tomato juice? I remember hearing this, don't know of anyone who has used it.

Muriatic acid, AKA hydrocloric acid,  HCl.  The friendly monoprotic acid.


Titration scares me.


klc
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« Reply #12 on: June 23, 2010, 11:45:37 AM »

One thing not to use is KOH or potassium hydroxide. It will react with the aluminum giving off hydrogen gas. What worked best for me was here at work called a Strahmann Station. They mix 140# steam with water making it ~190F cleans it pretty good. So, I would suspect a good dunking in boiling water would clean it pretty well.
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Ed/KB1HYS
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« Reply #13 on: June 23, 2010, 02:44:41 PM »

I think it was a memeber of this board who recommended simmering parts in tomato sauce and rinsing well. Claimed it worked gangbusters to clean a lot of metal parts.

I doubt I would accept an invitation to dinner there... Smiley
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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
Todd, KA1KAQ
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« Reply #14 on: June 24, 2010, 12:25:25 PM »

TNX, guys. Jim and Jay hit on what I think was the method used, just can't recall precisely (over 20 years ago). Jay's description of the final result sounds about right, the dull-but-clean aluminum look.

Hi Todd,
Sounds like your working on those Comet Pro shields!

You got it, Joe. That and a '36 SP-10 that looks like it sat by a chimney that leaked creosote onto the top of it. Apparently the cover was off. Sure is a mess, but with so few made, it's worth saving. The aluminum IF cans clean up well with elbow grease, I just want the final result to look more natural and less pimped up.

Sadly, the Comet might not fair so well. The deeper I dig, the more I find. At the least, it will be a good donor for a later rebuild, in which case some parts may be returning to your inventory.

Still beats the hell out of buying a 'restored' radio or paying someone else to do it for me, then claiming the glory. I enjoy the knowledge gained through hands-on experience, and God knows I could use it. Wink

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w3jn
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« Reply #15 on: June 24, 2010, 12:28:44 PM »

Try some Westley's Bleche-White whitewall cleaner.  I've yet to find something that stuff won't clean up, Todd.
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Todd, KA1KAQ
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« Reply #16 on: June 24, 2010, 12:34:06 PM »

I need to get some of that stuff Johnny, you've suggested it before. My only concern is ending up with a shiny/polished result instead of the dull, boring aluminum look. Then again, the early ads for the SP-10 seem to show shiny shields, so maybe that's how they came off the line?

So long as I can stem the corrosion and stabilize things, that's really all that matters.
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w3jn
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« Reply #17 on: June 24, 2010, 01:33:42 PM »

It's not gonna shine it, it'll just clean any grease/nicotine/crap off it.  It won't however, clean off corrosion.
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« Reply #18 on: June 25, 2010, 12:05:23 PM »

Some other options:

Sulphated molasses and water in a 5:1 to a water/molasses ratio. It takes about 10 days to clean a cast iron engine block and 12-24 hours for an aluminum intake, less for a carb or small chassis. It will NOT remove grease or paint.  For steel/iron only you can use a 4:1 mix.  Some have reported a 10:1 mix works on AL less aggressively. Temperature plays a big part, real fast on a hot summer day. Use it outside as it can get pretty ripe Roll Eyes Steel/iron will flash rust real fast on a hot humid day so paint ASAP or spray with Prep Step. It can also be used on AL, test some scrap first in all cases.

Get the molasses at a feed and grain store and the Prep Step at  http://www.zero-rust.com/zero-rust-prep-step.html

Carl
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« Reply #19 on: June 25, 2010, 12:57:58 PM »

Some other options:
Sulphated molasses and water in a 5:1 to a water/molasses ratio.
Carl

Is that what grandma used to call "black strap molasses?
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« Reply #20 on: June 25, 2010, 08:16:52 PM »

Only if she was a horse
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Don
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« Reply #21 on: June 25, 2010, 10:07:30 PM »

I once looked over a 75A-4 that had been refurbished by Howard Mills.  The i.f. cans and shield over the coil rack had a brilliant mirror like sheen, almost like a chrome finish.  I wonder what he used to keep the aluminium from developing that dull finish with exposure to the air.  Maybe the radio had just been completed and it hadn't had time to occur. Otherwise, it had to have had some kind of plating.
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Don, K4KYV                                       AMI#5
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« Reply #22 on: June 26, 2010, 10:49:50 AM »

Some years ago I polished the tube and coil shields of one of my early 30's Scott radios. Then gave a light coat of non yellowing clearcoat and they still shine as good as the day I finished them.

Carl
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« Reply #23 on: June 26, 2010, 03:14:27 PM »

Hi Todd,

These things always bring out a lot of solutions, and some of them actually work after a fashion, which is fine.  If you want the aluminum to look like it did coming out of the factory, then it's unfortunately a two step process, beginning with removal of any corrosion.  That may take some elbow grease, depending on the amount of damage.  I use Scotch-Brite pads (of two grades if necessary), ending up with an aluminum polish like Met-Al or Simichrome that will make it look highly polished.  Rinse with acetone.  If you like the look, then you're done.  However, if you want that factory look, then the second step is the important one - you have to use a proper aluminum etchant.  The most consistent I've found is available at your automotive paint store - Dual-Etch W4K263 Metal Cleaner and Conditioner by Sherwin-Williams.  It's concentrated, so you need to dilute it - it will look like clear water when you're ready.  Put it in a plastic container where you can completely submerge the part and keep it moving.  It is possible to use a paint brush or sponge and a shallow tray to continually bathe the part when it's too big to submerge, but you have to watch it like a hawk.  Bring it out of the etchant every 40-60 seconds or so and rinse it off for inspection.  When the polished surface gets that soft white look, you're done.  Rinse (use rubber gloves so you don't put oily fingerprints on the fresh aluminum) and dry thoroughly.  Then spray a liberal coat of WD-40 on the part and wipe it off with a clean paper towel.  The protectant in the WD-40 will prevent handling marks while the aluminum slowly oxidizes to that factory fresh look.  Yup, it's a lot of work, but when I worked in a plating shop, it was considered the only way to do the job correctly.  Most of the parts I've installed in the Smithsonian aircraft are prepared this way.

Remember that anything made of steel or brass will be etched at a higher rate.  Barrel nickel plated items like snap slide pins on command receiver covers will lose the plating if you etch for too long.  You can coat it with a masking fluid from an art store to protect them if you want to be careful about it.
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« Reply #24 on: June 26, 2010, 05:53:06 PM »

That sounds like a lot of work, but I'm sure the resukts are top notch. It would be great to archive that info so it won't get lost in the shuffle.

Don poses another good question about the highly polished stuff. I have used the clear coat method with varying results; sometimes it makes the parts look cloudy/dull. I've always thought that a good appication of carnuba wax would protect the lustre for a while. We all know the culprit of a corroded chassis/parts is dust and moisture. Periodical cleaning of the insides goes along way.

Phil
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