Hi everyone,
I have a question about a treatment that I am doing on aluminium parts, I have these aluminium (see image of the metalographic cut) pieces that I try to protect by anodization. After the treatment few pieces in my batch get black stains (see image) and I was wondering what it was due to?
I did a microscopic analysis after a metallographic cross section and i see these pocket of acid (I think) that may have solubilised the anodized aluminium.
I would love to have your opinion on that.
Which exactly aluminum alloy you tried to anodize?
Are the spots you have observed placed at the sample‘s surface? Have you a possibility to perform SEM - EPMA (EDS) examination to obtain idea about the chemical composition of these spots. Most probably, the sample’s surface was not cleaned properly prior to the anodizing.
Thank you for your input,
About the alloy I would not be able to tell you, but I might be able to get that information...
Yes I have planned SEM/EDS analysis to look at the composition. My first idea too was that the cleaning was not properly done and some "pitting corrosion" was happening.
I would agree that it is likely to be contamination of some type. What treatments (if any) have been performed on the material prior to anodising? I have seen similar issues on Aluminium alloys that have been shot peened with steel media and inadequately decontaminated prior to anodising.
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