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Cleaning Contaminated Anodized Aluminum

2002

We use anodized aluminum carriers in an assembly operation. Through the years, the carriers have darkened (changed color from a silvery luster to a dark yellow, green, brownish color) due to (A) transference of organics into the anodized layer by means of bare hand handling (oil from finger prints), (B) these carriers baked in ovens which were used for baking other organic materials, and (C) lack of cleaning since their introduction. Now, there is the possibility the carriers are outgassing contaminates embedded within the anodized layer, which in turn, contaminates strips (lead frames) that are transported in these carriers. When the lead frame surface becomes contaminated, the item which we want to adhere to the lead frame does not.

Question: What is the best solvent and method of cleaning these carriers without damaging the original anodized layer of aluminum oxide?

Question: Is the anodized layer impossible to penetrate with a solvent for cleaning out the contaminants embedded within the anodized layer?

Aaron Epstein
OSE - San Jose, California

Chances are that the outermost sealing layer has been compromised by heating or exposure to corrosive agents. If you are indeed adsorbing contaminants then either the parts were done cheaply (without a seal) or the seal is indeed damaged. Parts can't be repaired in situ and would have to be stripped and re-done. I would suggest that when the parts are re-done they be sealed after anodize in sodium dichromate or Teflon(R).

Milt Stevenson, Jr.
Plating shop technical manager - Syracuse, New York
2002

You may want to consider a coating that has no porosity. High Phosphorous Electroless Nickel has no porosity to trap dirt, withstands high temperatures and resists staining.

Todd Osmolski
- Charlotte, North Carolina, USA
2002

2002

Thanks for all your suggestions for sealing the anodized layer. They were:

1. High Phosphorous Electroless Nickel
2. Sodium dichromate
3. Teflon coating

Should we order new carriers, we will instill one of these suggestions.

Best regards,

Aaron Epstein
- San Jose, California

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