Metal finishing Q&As since 1989
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Alkaline Etch of Aluminum leaves a Marbled Finish
October 26, 2012
Q. I have been involved with metal finishing for a good number of years and never see it all.
In recent years, I see a marbling in some aluminum alloys (which I think are 6000 series) when alkaline etched prior to anodizing. I don't remember this from prior experience. Has anybody else seen this? How are you getting past this problem? Can you somehow know before processing which materials may do this?
AJE
- Denver, Colorado, USA
A. Andy
It could be the material or your etch. To rule out the etch, make up a 5-gallon bucket of your etch solution, and etch a part in each. If the test solution produces good results, consider decanting 30-60% (or all)of your etch and adding fresh chemistry.
A picture would help.
- Colorado Springs, Colorado
November 9, 2012
Q. Thanks for your input, Willie. I have captured a pic of this condition.
This has been addressed in another thread here and the etch argument has surfaces but not agreed upon. I am leaning towards a material problem that is becoming more rampant but not sure.
Andy
- Denver, Colorado, USA
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