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topic 4242

Debris, black anodizing, problems


My name is Scott Larson . . . a project engineer for Maysteel Corporation. I am not an anodizing guru, but know enough to be dangerous. My question is two-fold. First of all, is black anodizing a one step process where the coloring and anodizing occur simultaneously or is it colored separately? The other question pertains to this. We are experiencing debris in a hole which fits on a standoff. The problem isn't terribly costly for us, but it is a problem nonetheless. Is the debris acquired in the anodizing tank, or in the coloring tank? If we were to skip the coloring station could it eliminate this debris problem? Thanks for your time.

Scott Larson
- Allenton, Wisconsin, USA

First of two simultaneous responses--


hi scott. normally sulfuric type II anodize is first, immediately followed by black dye, and then a sealer is applied as the final step. please clarify the "debris" that is accumulating in the holes. is it aluminum residue left in the hole during the making of the hole? when you remove the debris following black dye, do you see bare aluminum where the debris had been? have you inspected the holes after each step of processing including pre-clean, etch and de-smut?

Bill Hemp
tech svc. w/ chemical supplier - Grand Rapids, Michigan

Second of two simultaneous responses--


Hi Scott,

Debris in the holes? Is it milky in texture? Like a "slime" almost or does it have more of a hard solidified state?

The thing I'm thinking is this:

If there are shavings trapped down in the hole it could be holding on to the anodizing electrolyte (sulfuric acid) and when given time to sit it will go from liquid to a sludge and this could be the "debris" you're talking about. Other than this, there is nothing I can think of that would come from a dye tank that would cause any sort of debris, or buildup of something in the holes. Basically a dye is nothing more than that, go to your local grocery/dept. store and check out the Ritz's dyes for clothing, same concept as on aluminum, just that the dyes for metals are slated for those purposes. The anodizing and dye steps are separate, with rinses and various other steps thrown into that mix (seals after the dye, etc.). The reason I mentioned shavings in the holes, I've dealt with it, and it does become a headache at times. Good Luck to you

Matthew Stiltner
plating company - Toledo, Ohio

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