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Reduce anodize thickness by leaving in tank with power off?

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probertEthumb Aluminum How-To
"Chromating - Anodizing - Hardcoating"
by Robert Probert

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Q. Type II Anodize of 7075 Aluminum. If the anodize is too thick is there a way to thin the coating safely without stripping?
I have been a chemical processor for 23 years and I am pretty sure you can leave unsealed aluminum in the sulfuric bath immediately after voltage is off for an extended time and the anodize will very slowly remove -- am I correct?

Ninj JJL
- Steelville Missouri
September 13, 2023

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A. Yes, it will be slowly removed if you do that...
But it will be also ruined, because the pore walls will erode in such a way as to leave the surface with a powdery "smut", which will be even more aggravated by subsequent sealing.

Sorry, there is no good way to partially "un-anodize" an anodized part's anodize thickness, short of stripping the coating and redoing it from the beginning.

P. H. Wheeler
- Czestochowa, Poland
September 14, 2023

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