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"Wormwood" pitting problem in hardcoat anodizing

September 10, 2015

We are having trouble with pitting on the face of some extruded 6061-T6 parts. The pitting shows up only after the hard coat anodizing and is on about 10% of parts from one batch of material and a few parts made from totally different material. Pitting is sometimes on both sides and is clustered. The worst of it appears in sort of a "wormwood" pattern.

wormwood pitting in hard anodizing

Is this galvanic corrosion or something else? I've read through others' posts and they are helpful. Can anyone suggest the most likely culprit here?

Chris Duppenthaler
- Bellingham, Washington, USA

Chris, what were the pre-treatment and post-treatment processes on the items? How many items are in a typical batch that goes through your process?

Blake Kneedler
Feather Hollow Eng. - Stockton, California
October 28, 2015

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