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Pin hole corrosion in 7075 Aluminum

 

What causes occasional pin hole corrosion in Anodized 7075 Aluminum?

Jerry Wahlin
plating shop - Compton, California

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Do you mean pin holes found after the anodizing process? If so, are the pinholes coming from the anodize or from some processing from before the anodize tank.

  
Tom Pullizzi
Falls Township, Pennsylvania
 

I would like to ask the same question . The corrosion is probably before anodize on machining parts

Moshe Yaakov
- Lod, Israel
 

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We can only anodize "aluminum", and if any of the alloying ingredients are left on the surface by inadequate deoxidizing then that spot does not anodize and becomes a "pit". Many anodizers swear by their pure Nitric Acid Deox but the proprietary deoxidizing formulations are designed to help remove the many different alloying ingredients far better than pure nitric.

Look at the base metal with a 10 X Loop. You will probably see the pits in the base metal before you anodize.

Any of the reasons listed in "White Spots" which is a letter shown by finishing.com may also be the culprit.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

 

We are using a Deox-Desmut product containing Ferric sulphate, Hdyrofluosilicic Acid/Fluosilicic Acid and having problems with deep pitting on 2000 and 7000 series aluminum. However, we do not see it until after the dye bath. I am wondering if this deox is not compatible with these materials? We did not have this problem before when we were using a straight nitric acid with an additive for our deox.

Dan Rose
- Oceanside, California USA
July 3, 2010