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Liquid Penetrant Inspection and anodizing

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One of our customers requires that a number of aluminum components be penetrant tested after machining to ensure freedom from defects caused by the machining process.

Normally this inspection is completed before the parts undergo a type 2 anodize. Unfortunately the fabricator chose to complete this inspection step after the anodize.

Is anyone familiar with technical reference material dealing with anodizing obscuring fine detail on manufacturing defects, particularly with regard to LPI inspection?

The coating thicknesses involved are very thin, and I could make the argument that the class of defects that would be detectable if not anodized, but hidden by the anodizing process would be a very small potential group, but something a little more concrete than idle guesswork on my part would be necessary before we take this to the customer.

The customer may choose to reject the parts, even if it turns out that we can make a strong technical case, but given the consequences involved, I think it's worth our while trying.

Thanks for any and all comments
 
According to Nondestructive Handbook, 2nd Edition, Vol 2, pg 336: "Anodic or chromate treatments reduce the brilliance of many fluorescent penetrants."

The anodizing should not have a detrimental affect on a visible penetrant inspection.

JR97

 
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