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"Hot spots" in anodize
August 5, 2011
I am having problem with parts from anodizer they say it is "hot spots". I think there are other issues. We can send 4 different parts out of same batch of material, 1 batch all parts will be bad. we are using 6061 T6 alum. Help
Greg
medical manufacture - Smithfield, Utah, USA
Greg
It looks like extruded material. I would expect you could see the cross section of the hot spot on adjacent surfaces, as well as the far side. Increasing surface finish (Ra) and reducing the pre-clean etch time can minimize the effect. Re-actively, you could re-finish after anodize with a scotchbrite pad on an orbital sander and blend it in.
- Colorado Springs, Colorado
First of two simultaneous responses -- August 15, 2011
1. Those spots could be where floating soil got into then pores before the seal, or 2. Since the spots are elongated in one direction, it could be the rare thing that happens when you anodize "cold drawn material".
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
Second of two simultaneous responses -- August 15, 2011
These parts are being run on a conveyer system at the anodizer; we do not see the spots all the way through the part most of the time they are only on 1 side.
Greg Carter- Smithfield, Utah
August 18, 2011
That can be grease. Maybe the anodizer didn't make the proper degrease bath before the soda treatment.
Richard Martinez- Guadalajara, Jalisco, Mexico
August 23, 2011
December 20, 2011
We've had similar problems with anodizing from our most recent vendor. However, the patterning in our parts is much more rampant than the original poster's. We see this type of patterning on about 80% of these parts that we get back. The picture shown is a worst-case.
The anodizer can't give us any clear answers on why we see this type of pattern, although they did claim that it was something occurring in our processes. We do not process these differently than any of the 50 or so other part numbers we send them, but these are one of three parts that exhibit this type of patterning. It's probably worth mentioning that the material is 6061 Al, the grain direction is in the long dimension, and we use Blasocut 2000 in our mills.
Anyone have any input aside from what has already been offered?
- Denver, Colorado, USA
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