The AM Forum

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.

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
K5WLF

Muratic acid, but be cautious and handle with care.

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
WD5JKO

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.       

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

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.

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

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?   

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.

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      

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

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.

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... :)

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.


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. ;)

Try some Westley's Bleche-White whitewall cleaner.  I've yet to find something that stuff won't clean up, Todd.

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.

It's not gonna shine it, it'll just clean any grease/nicotine/crap off it.  It won't however, clean off corrosion.

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 ::) 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

Is that what grandma used to call "black strap molasses?

Only if she was a horse

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.

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

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.

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

Thanks for the thorough description, Mike. If it's good enough for the Enola Gay and her siblings, it's certainly good enough for the few clunkers I have around here.  ;D

I know that much of this sounds like a lot to go through for some old piece of radio gear, and in most cases I wouldn't bother since many of the rigs here are relatively commonplace. It's only when an interesting and equally-scarce set appears, generally of 20s-40s vintage that I bother with any excess. The fact that it's as old as it is and still around warrants slightly different handling, IMO. There are (literally) tons of S-38s, KWM-2s, and many other, newer rigs out there. Not so with the early super rigs (for their day) like the SP-10, Comet Pro, and others.

The biggest issue now is the slight amount of damage through corrosion, crud, and a few doinks that need to be removed first. Once that's done, restoring a uniform color/finish to them will let them blend back into the chassis like the basic components they are. Unlike some of the flashier sets with chromed chassis, IF cans and tube shields, the Hammarlund gear was all go and less show.

Figured I'd add a couple shots of what I'm up against. Getting the crud off first is a must, then removing dings and as much of the scraped in labeling as possible before running the aluminum through the chemical bath.

Although it looks really rusty, much of it appears to be creosote or something that dripped into the receiver over time. It has a tar-like consistency and comes off pretty easily. Fortunately the entire tuning box is removable which will make cleaning up the main chassis much easier. The metal cover was in place and lost paint in places, so it looks like the crud seeped in between the panel and cover, and dripped inside for an extended period of time. Getting the bazillion little screws loose on the inside top covers was a LOT of fun.

Not much hope of it ever looking new again, but that's okay. It's complete and unhacked, a survivor since 1936. It's earned the right to wear its character marks, minus the dirt and crud. :)

       


          Geez, that's one dirty radio... Thats not the one you got from Buddly,
          is it ?

Hey Ralphie!

No, not even close. The BudPro as I sometimes call it, is a SP-100 and in like-new condition compared to this one(see below). Was thinking you got to see it at Frank's party a few years back? This is its predecessor, the SP-10 - first of the Super Pros and successor to the Comet Pro. It lacks the crystal filter of the 100 and also has adjustable detector and AVC transformers (along with the more familiar adjustable selectivity IFs) for more flexibility, though you have to remove the cover each time to adjust them. A flip-top door would've been nice, but I suspect they figured you'd set it up for the type of service you were using it for (narrower CW vs. wide AM broadcast, for example) and leave it that way. You can see the knurled nuts atop several cans in the back.

They didn't make a lot of the 10s, moving to the 100s in the first year of production. So there were never many SP-10s to start with, between the low production numbers and high price for depression-era folks.

If you think the SP-10 looks rough, you should see the Comet Pro. The deeper I get into it, the more it looks like a parts donor for a better candidate. The SP-10 is pretty straight overall, cleanup being the bigger challenge.

there has been previous discussion about boiling that stuff in tomato sauce to clean it. The Dago in me makes me want to try it. After all anything is better wen served with tomato sauce and pasta!!  ;D  ;D

     Frank, you have a point, marranara acid will clean anything...

     Todd, I didn't think bud would let anything like that radio out of
      his grasp.  That thing is really grungy...

      Thinking back, yeah, I saw buds SP-100 there at Franks a few years
      back, think it was the same year I left my SP-400 with Frank (he
      still has it!  wink wink - hint hint)...

      

My problem with is that it is a waste of perfectly good tomato sauce. Think of the pasta it could cover!

IIRC, Ralphie, I said it would be quite a while before I got to it.
Also I wasn't expecting to die back in december :o  :o I havent even had the ambition to work on my own stuff. But, maybe that may change around a bit now.

thatz the problem with us dagos. We'll throw just about anything into a pot of sauce to give it flavor. I used a half a dozen 4-400s in the sauce for the lasagne for the party. I figgered it would be a fitting flavor enhancement for a bunch of fellow AMers  ;D  ;D

Hmmm.................I wonder if I used an old Super Pro, would it be super sauce??  ;D ;D

        Yes, I remember what you said Frank...  No problem, just joshing...

         However stuff happens and we are all glad you  managed to work
         your way back  from that December episode...

         I never in my wildest dreams expected to be around this long, figured
         I would get shot  by an irate husband while in bed with his wife but gee,
         in 32 days I'll hit the 83 year mark. (There has been a couple close calls)

         Anyway you look at it, there can't be too many more on the horizon...

That or ProSauce, Frank.  ;D  Mike(y) has a point, no need wasting perfectly good sauce on something a simple checmical bath will take care of!


Neither did I, Ralph. I remember when he told us about it on the air one night, and later posted some photos on 'fone. I expressed my interest should he ever decide to part with it, but at that time it wasn't going anywhere. Maybe a year later a nice R-390A came his way, so he contacted me to see if I was still interested. Didn't take me long to answer! Other than a couple of older mods (tube upgrades, but at least they stuck with octals), it's in really nice shape and Bud cleaned up the panel and cover really well. It's currently my bedside receiver for listening to AM740 out of Ontario. Drives a big Jensen coaxial speaker in an old EV enclosure.


Reminds me of one of Paul Newman's lines from the movie HUD:

"The only question I ever ask any woman is 'What time is your husband coming home?'"

I gotta say Ralphie, you sure had me stunned when you told me your age some years back, after talking with you on the air and later meeting you. Pretty damned spry for an old guy! At this rate, you'll outlive most of us. ;)