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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing 1989-2024
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Anodizing: Small Area That Doesn't Dye
Q. Hello,
I am having an issue, across different parts, in different spots, where one little area will have a dye blemish. For instance, in the last batch of 12 parts, 2 had blemishes in different spots (the one not pictured was not near a hole of any kind). All were prepared and processed the same way.
Aluminum How-To"Chromating - Anodizing - Hardcoating"
by Robert Probert
Also available in Spanish
You'll love this book. Finishing.com has sold almost a thousand copies without a single return request :-)
Things to note:
-area is showing no continuity
-area looked even goldish silver when coming out of anodize bath. No obvious visual issues before dye.
-When it first happened, I thought it was a cleaning issue, so I scrubbed and soaked in dish soap (which I usually do), and left parts in our anodizing degreaser overnight, still had issues.
-Dye bath is fresh for the last batch that had issues.
-thoroughly double neutralized acid before dye to be sure.
It could still be a cleaning issue, but it's so difficult to believe that deep threads, where grease is likely to hide, are anodizing fine, but random surfaces that are easily cleaned are having grease blemishes?
I plan on replacing the degreasing solution and my rinse tanks, but other than that I'm a at a loss?
Machinist and Anodizer - Lansing MI
November 15, 2024
Q. Just an update, I ran 7 parts in Gold, no issues. I also ultrasonic cleaned these parts before the degrease tank. It is looking to either be a cleaning issue (most likely, even though I didn't want to believe it) or an issue with the black dye. Will update when I dye parts black again.
Logan Heddens [returning]Machinist and Anodizer - Lansing MI
November 22, 2024
Ed. note: Thanks!
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