Metal finishing Q&As since 1989

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Brown Stripes on Aluminum after Anodizing

Hi all, hoping that someone has either seen this before or can at least lead me to the right direction. We had some aluminum 5052 sent out for anodizing and some of the pieces came back with a brown stripe. the stripe is only on one side and is not uniform. It can be 1/4" wide up to 3" wide, a single stripe or 3 or 4 separate stripes. It is not on all the pieces just some random ones. The parts were laser cut and the striping does not line up as if it was the material that caused the striping. There were also no marks on the aluminum before it went to be anodized. We sent some other parts from the same laser batch to a different anodizer and no stripes. There are about 60 pieces and each is also a different colour.

Joseph Eade
production manager - Winnipeg, Manitoba, Canada
June 1, 2011

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July 8, 2011

Hi!
If possible, can you pls post a full picture of the part, away from its packing and all...especially in the same state as it went to the anodiser.
And highlight where the contact marks are on the part, where the anodiser would have clamped it to the jig.

Ravi

Ravi Rao
- Belgaum, Karnataka, India

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July 12, 2011

Joseph

If you can afford to, have one of the 'striped' parts stripped. If you can still see the stripe, it would suggest that it is a material-related cause as opposed to process.

Does the stripe run in the same direction as the material grain?

Willie Alexander
- Colorado Springs, Colorado

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Ed. note: Where ya been, Willie -- we've missed ya.

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Hi Guys,

Thanks for the responses. We have actually solved the problem by sending the parts to a different annodizer who has stripped them and refinished them. The new parts have absolutely no markings on them, and are actually a uniform color (which the others were not). Seems it was a problem in the process somewhere not the material as was my first thought.

Joseph Eade
- Winnipeg, Manitoba, Canada
July 21, 2011

The marks seen on the photo may be from the racking material that shadowed during the process. Such as aluminium wire to rack the extrusion to the vertical spline of the load bar.

Timur Ulucak
- Istanbul, Turkey
July 27, 2011