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topic 8357

White Patches on Clear Anodised Parts


Q. We have a clear anodised 6063 Al case that have white patches on the surface. What's the possible cause for that?

WY Wong
- HK


A. If the white deposits are marks/stains UNDER the anodising, they could be due to water stains/corrosion BEFORE the anodising process. Please post a few more details. Do you carry out the anodising? or are these 'cases' products that you receive?

Best regards,

Martin Webb
- New Zealand


Q. Our anodizing frame (6061 aluminium material) has the same problem. We have a white spot or pine hole deposit on the surface. How to prevent this problem.? Anyone can help?

Dai Nguyen
- Sunnyvale, California, USA


A. I have to agree with Martin. More details are needed. White spots can be caused by a number of things. Have you discussed this with your anodizer? I would start there, possibly they can aid you in minimizing this condition!

Good luck,

Bill Grayson
- Santa Cruz, California, USA


Q. The pieces I'm talking about are anodised by a local vendor. It's actually a 2-toned piece, meaning 2 colours(clear/olive) on the same piece with a masking procedure. The olive colour looks alright, but the clear part has milky patches, I don't think it's under the anodised layer, as these are decorative parts, the problem's quite serious. We've talked to the anodiser but they've no idea(or they have but won't admit it). We actually have loads of problem about anodising, like inconsistent colour, uneven colour, colour fastness. We've changed vendors but troubles just keep popping up.

WY Wong [returning]
- HK


A. White Patches is very different from white spots. Both problems can be caused by a lot of factors, i.e. contamination /inadequate rinsing . White spots can be the cause of galvanize corrosion and white patches may mean inadequate cleaning. You need to identify the step in which the problem occurs from. There are some good anodizers around your area which could give you better services.

Please contact us.

S. Y. Yuen
- Hong Kong, China

January 26, 2016

Q. Hi, I would like to ask about possible root cause of the white patches and rainbow effect on surface of a 6061 material. The material was processed for Hard Clear Anodizing with Hot DI Water Seal for 160 minutes.

The white patches was actually not observed after anodizing. It was intercepted after it was transported already to end customer. What could be the cause of this defect?

The rainbow effect, was already evident after anodizing. Is this due to the sealing process?


Yma Bonao
- Singapore

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