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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Shot Blast Aluminum Casting for Dark Color
Q. How could we get the aluminum casting a dark surface by a fine stainless steel shot blast? Thanks
- Shanghai China
December 1, 2020
? Hi Jim. I've personally never heard of such a thing, and if it is possible I'd like to hear about it too :-)
But if you are saying you want to anodize to a dark color after bead blasting, the following threads may help:
• Thread 44324, "Bead Blasting of Aluminum: Specifications, Q&A, Problems & Solutions"
• Thread 42754, "Anodizing to a matte black finish"
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. If I'm not misunderstanding the question, and that the shot blast is a prep step, and you're going to anodize it as the final surface treatment, I'd personally skip the stainless shot and go directly to aluminum oxide, except the finish will be more matte. You can always follow it with a satin mask step (bifluoride based mildly acid etch sold for bright frosty finishes, but without the added nitric ) to restore some smoothness and a slight sheen.
Bonus, parts treated this way will then take well to dyes, and you can get anything from midnight black to whatever shade of dark grey you're after. Just pick a dye with the right undertones to balance against the natural finished color of your alloy when it anodizes.
If the shot blast IS your final treatment, disregard.
Rachel Mackintosh
lab rat - Greenfield, Vermont
December 3, 2020
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