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Non-sealed Anodised AA5 is staining through our powder coating

Hi I wonder if any one can advise why after four years of using Anodised AA5 non sealed as a base for powder coating, we are getting almost invisible stain marks which after powder coating show up on stain, we then have to buff down and re-powder coat, it looks like run marks, I wondered if it was being packed before dry ?
It is the same anodiser and we only get it from time to time, they claim that is the risk when using non sealed, that it can start to seal.
We had sections out all winter for six month we then did a dye test and it had not sealed
Has any ony had this problem?
Best regards

Richard Rinn
powder coating - Scotland
June 25, 2008

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Go challenge the purity of his final rinse. Sounds like impurities in the rinse water is cooking back out of the anodizing pores. Stand at the end of the line and spray a few parts with a hand squeeze pump filled swith grocery store distilled water, powder coat, let us know.

IF that fails, then challenge the dissolved aluminum in the anodizing tank. Should be under 12 gmL. Dip some parts thru 5%./vol Nitric Acid, then spray off with distilled water, let us know.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

June 26, 2008