Letter 14018

7075 aluminum pin hole corrosion [California] 

I am looking for articles and research re pinhole corrosion problems that occasionally appear after anodizing 7075 Aluminum.

Jerry Wahlin
PLATING - COMPTON, CA, USA

If a search of the finishing.com website doesn't help, try the platronica site, and click on library notes, it is a very big page, but you could look over some of the articles over the years on aluminum and anodizing for clues.

Tom Pullizzi Platronica.com Falls Township, PA

Try a mixed acid proprietary deox that will get more zinc out of the surface.

Be sure the anodizing solution dissolved aluminum is under 12 gm/L

Use a 5% Nitric Acid Dip between the anodizing and the seal to remove sulfates, zinc, and dissolved aluminum out of the pores so that the seal will be better.

Seal must be PERFECT - deI, no calcium.

If you can stand the color, the best corrosion resistance you can get is with a potassium dichromate seal.

Take two aspirin and call me in the morning.

Robert H Probert Robert H Probert Technical Services Garner, NC, USA Editor's note:        Mr. Probert is the    author of Aluminum How-To

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