Cleaning cast aluminium

Discussion in 'Castings, finishing/ repair/ and patina's' started by Oxide, Feb 26, 2018.

  1. Oxide

    Oxide Lead

    Afternoon chaps,

    Do you guys have any tips on cleaning aluminium castings

    I've got a few castings that are a bit dull, try'd soft brush and soapy water but to be honest it now looks worse

    I have heard of citric acid but not sure...
  2. Jason

    Jason Silver Banner Member

    Bead blast. Citric acid should remove the black you probably created while cleaning.. Got a photo?
  3. A hit on the bench grinder wire wheel works wonders for new and old castings, taking care to be gentle and not smear aluminium by being too rough. A scotchbrite wheel on a spindle is pretty awesome for any type of casting: rusty iron, brass, aluminium.

    I did the castings below with a scotchbrite wheel and then a run on the buffing mop.

    Sher dril press lhs.jpg
    Sher nameplate.jpg
    Sher drill press motor fixed.jpg
    Sher painted.jpg
    Last edited: Feb 26, 2018
    Oxide, Jason and _Jason like this.
  4. DavidF

    DavidF Administrator Staff Member Banner Member

    I like blasting them with steel shot for that "cast" look.
    Scotch bright wheels are great too!
  5. Jason

    Jason Silver Banner Member

    But MAN are they pricey! That drill press above looks awesome. No one will ever spend 100hrs restoring a HF drill press.... EVER!
  6. DavidF

    DavidF Administrator Staff Member Banner Member

    Yes but they last alot longer than you would think, so that makes them inexpensive ;)
  7. Jason

    Jason Silver Banner Member

    Amazon to the rescue. Thanks!

    oh... FWIW, simple green should cut that black crud that builds up. When I polish aluminum, I do it with a bucket of soapy water for my wet sand paper.
  8. Oxide

    Oxide Lead

    Holly crap that drill looks pimped

    Ok looks like scotch bright is the answer thanks
    Last edited: Feb 26, 2018
  9. Just a disclaimer: that's a new hard chrome column and Jabobs 1A chuck on that drill press the rest is original iron and aluminium castings.
  10. Tobho Mott

    Tobho Mott Silver Banner Member

    I've used "Mother's Mag Aluminum Polish" to give a few aluminum castings that little extra bit of shine on one or two occasions.

  11. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    If all you want to do is clean the casting I use a light (not stiff wire) stainless wire brush either by hand or on a wheel. If you use a carbon steel brush or shot, sometimes you can get material transfer and the oxidized steel (rust) can later appear on your aluminum casting surface over time.

    If you want to cut, polish or otherwise disturb the as-cast surface there are many options from media blasting, tumbling, abrasives, and combinations of the two and they all provide uniform color to a degree. When you blast with abrasive media you should expect some of the media to imbedded in the aluminum surface. Blasting the inside surface of an engine part with glass beads is a bad choice because the imbedded glass will eventually find it's way into your lubrication system. Stainless steel shot has less tendency to transfer but rust on carbon steel shot does.

    Dilute Phosphoric or hydrochloric acid will also etch, clean, and color but it may work threads and sharp edges more aggressively than the rest of the casting. If you don't want to disturb the casting surface and just remove dirt and grime, I like blasting with walnut shells.


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