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Can we check for clear chromate by yellow chromating?

If a part has been treated with Clear Alodine and you stick it into a tub of Gold Alodine, should it come out gold or stay clear? My company is telling me that if the Gold Alodine sticks that it is an indicator that the part has not been treated with Clear Alodine previously.

Thanks

Justin Venlet
Quality Assurance - Sacramento, California, USA
May 19, 2010

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Justin,

I agree that a yellow chromate would not take over a clear chromate, but it would be a mad way to try and prove if you have clear chromate. There must be a reason you are accepting clear chromate, not yellow chromate and dipping in yellow chromate could potentially make your parts non-compliant. I would check with your customer before embarking on any such test if I was you.

Brian Terry
Aerospace - Yeovil, Somerset, UK
May 20, 2010

What we are receiving is small aluminum sheets intended for use as paint witness coupons. When they were received, the question was raised as to how to determine if they were actually treated or not. Our resident plating guy said the only way he knew was to dip it one in yellow Alodine. Apparently, some of them came out yellow. If they really were clear Alodined, then what we are thinking is that they would come out clear, as the yellow Alodine shouldn't stick on the already sealed surface. Correct?

Justin Venlet
- Sacramento, California, USA
May 25, 2010

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Justin,

Correct, unless there is incomplete coverage of the clear chromate.

Brian Terry
Aerospace - Yeovil, Somerset, UK
May 28, 2010