Metal finishing Q&As since 1989
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Zinc Plating + Iridescent Chromate expected, but parts are white
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Q. I am the QA of my company.
Recently, our company received electroplated products (Zinc + iridecent chromate) from the electroplating factory, and found that the appearance of the products is not the same as before.
(previous appearance = silver and shiny)
(now appearance = whitish)
What is the problem with the white color after coating?
After checking with the electroplating factory, they explained that this blushing is due to the color change after rainbow chromate, and the zinc plating thickness is between 10 µm and 13 µm, which is still within the drawing specification.
- Puchong Selangor
June 2, 2022
A. Dear Lucy,
The iridescence of the zinc plated parts depends on:
-Concentration of the chromate (the more the concentration, the more iridescence)
-pH of the chromate (the lower the concentration, the more iridescence)
-Organic content of the zinc plating bath (the lower the better)
-Thickness of the plate (the more the better)
-Whether there is or isn't a sealing process afterwards (if there is, you won't be seeing any iridescence).
All this, when you see iridescence then you can tell there is a thick chromate layer. When you don't see it, you can't tell.
Hope you get what you purchased!
Best regards,
Quality Manager - Cañuelas, Buenos Aires, Argentina
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