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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.

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?

Logan Heddens
Machinist and Anodizer - Lansing MI
November 15, 2024