How would I remove etching from aluminum?

Discussion in 'Shock Brother's DIY Amps' started by brokenbones, Apr 5, 2020.

  1. brokenbones

    brokenbones Tele-Holic

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    Are there any inexpensive ways to refinish etched aluminum? I'm building an attenuator with a repurposed chassis that has an etched faceplate. I'd like to remove the etching in exchange for simple decals. The etching isn't too deep but i'm wondering if sanding it down and buffing it out is feasible or worth the hassle? Anyone have experience on the matter?

    Thank you.
     
  2. BigDaddy23

    BigDaddy23 Tele-Holic

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    It will sand out if it is relatively superficial - hit it with a random orbital and it will be job done in a few minutes.
     
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  3. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    How deep is it?. It may be easier to apply a 'fishscale' over the whole thing, or if it isn't too deep, mock up a brushed finish with a sander then Scotchbrites.

    Could the etching be highlighted as a sort of retro-reuse cool, or shabby chic aspect of the design itself?
     
  4. trev333

    trev333 Telefied Ad Free Member

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    Here's some control plates made from Ali.... sanded back through the fine grades and polished as far as you want to go... these ones are not buffed on a wheel...just elbow grease...;)

    the longer one needs a bit more work... I was keen to see how the bass sounded and didn't get around to polishing up too much.......or worrying about a tone control...

    it's dirty to work on sanding.. you get black on your hands... and should be sealed to stop oxidation in future...

    control plate1.jpg

    control plate 2.jpg
     
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  5. brokenbones

    brokenbones Tele-Holic

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    I took some photos... The etching doesn't appear deep at all but then again i'm no metal expert. The only part of the etching i'd consider keeping is the single line border.

    [​IMG]
    [​IMG]
    [​IMG]
     
  6. trev333

    trev333 Telefied Ad Free Member

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    I'd call that a Brushed finish.... stainless can get a finish like that as well...

    how you do it and keep the line would be tricky....
     
  7. tery

    tery Poster Extraordinaire

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    Fine emery cloth with a small wood block - it won't take you long .
     
  8. trev333

    trev333 Telefied Ad Free Member

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    would paint stripper remove the writing to leave a clean surface ?

    is that what you need to do, just remove the old black writing ?
     
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  9. brokenbones

    brokenbones Tele-Holic

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    I tried some acetone and it didn't remove the lettering at all. If the paint is removed the etching will still be visible to some extent. The goal is to sand it down as fine as possible and buff it out until it shines.
     
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  10. chas.wahl

    chas.wahl Tele-Meister

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    My guess from the photos is that your faceplate may be anodized.
    https://en.wikipedia.org/wiki/Anodizing

    If that's the case, it can be removed with a caustic soda solution (base, sodium hydroxide, NaOH), such as oven cleaner. It's important not to overdo this -- better to do it twice than overdo it once. The resulting aluminum finish will likely be dull and/or patchy, so mechanical abrasion (using successively finer grit) will be necessary to make the finish consistent. It's certainly possible to remove the anodization by mechanical means only, but the anodized layer is harder than the base metal, so less metal loss may happen by removing that layer chemically first. Also be aware that anodization consists of an oxide formed on the surface, plus the same effect reaching into the base metal for some microscopic distance, like hair follicles in skin. To truly get down to base metal only, you need to remove some of the base metal too.

    Removing Anodizing from Aluminium with Oven Cleaner


    Removing Anodizing From Aluminum Quickly and Easily {using a degreaser product)

    https://www.instructables.com/id/Removing-Anodizing-From-Aluminum-Quickly-and-Easil/

    Disclaimers: I don't have a degree in metallurgy, but I have removed anodization from bike parts with some success, using the first method linked-to above. Be careful! Use eye protection and skin protection, and avoid touching parts or solution(s) used -- instead use implements, and don't spray water around. Instead, rinse gently in a bath, several times if necessary. Make sure that containers are plastic, not metal.

    I've found with bike parts that waxing the finished product seems to provide reasonable protection from further oxidation (which looks whitish on aluminum); needs to be renewed occasionally, but easy to do. I also recommend Simichrome polish as a final cleanup (fine abrasive with a bit of oxalic acid), though BonAmi (feldspar and soap) or Barkeeper's Friend (feldspar, linear sodium dodecyl benzene sulfonate (DDBSA) and oxalic acid). may be just as good.
     
    Last edited: Apr 5, 2020
  11. brokenbones

    brokenbones Tele-Holic

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    @chas.wahl Thank you for that post. I did some digging online and this is what I came across on how to test whether the aluminum is polished or anodized.

    "An anodized surface will show essentially infinite ohms" and "if there is continuity, there is no coating"

    Also...

    "Scrape a penny across an unobtrusive portion of the metal.If the penny is able to scratch the finish, the material is polished aluminum. If the penny leaves a streak of copper on the item, then the surface is harder than the copper and the piece has been anodized."

    The results of these tests were that the penny did not leave copper, only a scratch. Continuity and an ohm reading other than infinite required swapping my 'needle point' leads for a set of thicker alligator clip leads. A small amount of pressure had to be put on the test points in order to get these results. Am I safe to assume that the surface is polished and that polished metal is slightly less conductive than unfinished aluminum? Or could it be there IS a small layer of anodization on the metal? Would caustic material be necessary to remove such a small layer?
     
  12. sds1

    sds1 Tele-Afflicted

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    There are laserable brushed aluminum sheets available. They engrave to black in the same way you see here.

    Could be.
     
  13. chas.wahl

    chas.wahl Tele-Meister

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    I wish I could tell you, but I can't. My experience of this is with bike parts only, where it's pretty obvious what's anodized and what is not. I might be able to detect a difference if I saw the faceplate in person, but I have no confidence in being able to do so in photos. My impression is that bare aluminum has a slightly "colder" color appearance than clear anodized aluminum.
     
  14. Old Deaf Roadie

    Old Deaf Roadie Tele-Afflicted Silver Supporter

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    Wet sand aluminum with 220-240 grit on a block & common rubbing alcohol. It will go quickly & clean up nicely.
     
  15. printer2

    printer2 Poster Extraordinaire

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    Sandpaper, the aluminum would find it hard to resist.
     
  16. FenderLover

    FenderLover Poster Extraordinaire

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    Sand it, then put a wire wheel on a drill to re-brush it to uniformity.
     
  17. AAT65

    AAT65 Friend of Leo's

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    Alumin(i)um is a very reactive metal: there is virtually always a thin layer of aluminium oxide on the surface of any exposed metal.
    Anodisation just forces the growth of a thicker oxide layer.
     
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