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Aluminum anodize coating failure due to air ionizer?

My company has an interesting situation. We manufacture measurement systems for use in cleanrooms.
We are getting reports from the field that the anodize coating on a part is failing. This failure is in a area approximately 4" below an ionizer bar used to limit static electricity build up. The failure is consistent between 7 (so far) separate machines in cleanroom atmospheres.
Is it possible that the ionizer used is causing the anodizing process to be reversed?
For us this could be an enormously expensive recovery; we are looking at every possibility.

Thank you,

Don Porter
OEM manufacturing - Holliston, Massachusetts

First of two simultaneous responses --

Maybe this could help: If the function of the Anodized Surface is to insulate or not pass current, then ionizing the air around the anodized surface defeat its insulating function. Ionized air is conductivE or passes current.

Joseph V. Franco
- Manila City, Philippines

Second of two simultaneous responses --


What do you mean by failure? Are all of the effected components anodized by the same supplier? Do you have a picture of the failure? Is this failure a new problem in an existing system, or is the system new?

Willie Alexander
- Colorado Springs, Colorado


I apologize for my delay in replying.
My failure is; an area of black anodize approximately 3.5" long (horizontal) and 1.5" deep (vertical)is deteriorating and the anodize is flaking(dusting?) off. It can be removed with a cloth wipe.
The area is centered within the ionizer pins which are approximately 4" diagonally away from the surface. The pins point downward and the anodized surface is vertical.

The function of the coating is mainly color and seal the aluminum body to prevent cleanroom contamination.

Thank you for your replies.

Don Porter
- Holliston, Massachusetts

You may want to consider that something in the air is being ionized and attacking the anodize. Fluorine containing elements would be ionized to F then F would preferentially combine with H (from H2O) to make HF. This would definitely attack the AL2O3.

Sean Casarotti
- Yreka, California, USA

To clearly understand the problem, the process followed and the photo of the component showing the defect is required. however the following points may be given a thought.
1. if the material is a casting and the bath is of sulfuric acid the problem of getting a powdery deposit,in course of time which can be wiped with a cloth will be there. solution is go for a chromic acid bath.
2. after anodisation a supplementary coating of an organic glue with option of mixing the coloured die may enhance the quality of the anodisation.
.care may be taken in the preparation of the substrate at the area where the problem is expected to come.


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