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Light Fast Test for Checking Black Anodising

I recently had a huge problem with black anodising turning purple which turned out to be a sealing or "lack" of it issue. As a result I would like to be able to test the parts quickly and have heard there is a light fast test using nitric acid that can be carried out quickly. I have also heard there is a standard test of light fastness using UV light. I would appreciate any help that you can share!

David McKinney
- Northern Ireland
2005

I'm not familiar with a UV test for sealing. However, a very simple test (to check for seal quality) for dyed anodized parts, is to place a drop or 2 of 40% (vol) nitric acid on the anodized surface for 2 minutes. After rinsing, if there is a white spot, or noticeable discoloration where the acid was, that usually means the parts werent sealed properly.

Marc Green
anodizer - Boise, Idaho
2005

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