Weird stain or oxidization on silver face knobs (don't use HF ultrasonic cleaner on aluminum knobs)

dlucy

dlucy

dlucy67 (Doug)
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EDITED to quickly point out the risks for anyone considering using an ultrasonic cleaner for aluminum or anodized parts like knobs and push button covers:
  • Harbor Freight HFT ultrasonic cleaner (powder stuff) specifically states in small print it will eat through aluminum
  • Even ten seconds in an ultrasonic bath will damage or mar the finish on anodized parts (and there is nothing you can do to fix it)

I've cleaned up a set of knobs from a silver face Pioneer using an ultrasonic cleaner... and ended up with some very strange, stubborn stains or oxidization left behind.

IMG_2139.JPG

The stains have resisted further cleaning with silver cleaner/polish and plain dish detergent and water. I'm considering hitting them with silicone spray in case this is some issue with inadvertently removing necessary oil from the metal... but that has me thinking I'm crazy.

Have any of you seen this before? Have recommendations for how to fix the knobs and return them to their original look?
 
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4-2-7 said:
You wrecked them, aluminum parts are anodized so they stay shinny and don't oxidize. The cleaning you have done harmed the clarity of the clear anodizing.
Click to expand...

:( Rats. I was afraid I'd hear that.

Can such parts be re-anodized?
 
Not what I wanted to hear, but thanks for explaining it. Gotta keep telling myself "Learning is fun, learning is fun..."
 
i've been using ultrasonic cleaning on knobs and small parts for a few yrs
just dish soap and warm water, never had that happen.
perhaps the stains were there before hand?
 
At this point I would wheel buff use a stainless brush and polish.
Or you could try a tumbler corn/cob media..org. finish will be gone and looking matt.

Best-

Boozehound
 
You might some mothers mag and rim or other similar polish on them using a buffing wheel or elbow grease as a last resort.
 
There is very little you can get your hands on that will attack anodize directly. Unanodized aluminum is easily attacked by alkaline cleaners quite easily, but they wouldn't leave the knobs shiny. Are you sure they weren't overcoated with a clear lacquer or something similar? Since they're already messed up, I'd see if he deposit is affected by lacquer thinner. If you can clean them up, they can be resprayed, or maybe hide the damage with a clear coat the way they are. Stripping and reanodizing would probably be a disaster, as few people here can give you a finish that looks anything like the original. If it comes to it, there's always black powdercoat!
 
dlucy said:
I've cleaned up a set of knobs from a silver face Pioneer using an ultrasonic cleaner... and ended up with some very strange, stubborn stains or oxidization left behind.

View attachment 911011

The stains have resisted further cleaning with silver cleaner/polish and plain dish detergent and water. I'm considering hitting them with silicone spray in case this is some issue with inadvertently removing necessary oil from the metal... but that has me thinking I'm crazy.

Have any of you seen this before? Have recommendations for how to fix the knobs and return them to their original look?
Click to expand...
as a final recovery try some wd 40 , it sometimes can blend the milky look to a shine and at least be presentable.
 
this has always worked fantastic for me, nothing really any less painless.
 

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Looking at the caution "Not for use on aluminum or magnesium alloys." Then grabbing an MSDS for an ultrasonic cleaning power, that one(not known if it is the same as HF type) contains potassium hydroxide and that can attack aluminum and may have destroyed the anodizing layer on the knobs.

Good thing is the knobs are from the most ubiquitous stereo gear made back then and you should be able to find em on the bay sooner or later, with or without a unit attached.
 
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We used to use a cleaning solution at work that was very effective. We switched because people kept putting aluminum in it- it had potassium hydroxide. You could completely dissolve small parts if you left it in long enough. Best case, they were really ugly.
 
ConradH said:
There is very little you can get your hands on that will attack anodize directly. Unanodized aluminum is easily attacked by alkaline cleaners quite easily, but they wouldn't leave the knobs shiny. Are you sure they weren't overcoated with a clear lacquer or something similar? Since they're already messed up, I'd see if he deposit is affected by lacquer thinner. If you can clean them up, they can be resprayed, or maybe hide the damage with a clear coat the way they are. Stripping and reanodizing would probably be a disaster, as few people here can give you a finish that looks anything like the original. If it comes to it, there's always black powdercoat!
Click to expand...

i worked a chemical plant for yrs, it was mostly stainless steel and we used thousands of kilo's of 50% caustic soda for cleaning weekly.
the whole plant would get a caustic wash.
you should see what happens to aluminum shovels, from blackened and smoking to almost dissolving
 
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