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Measurement method(s) for coating thickness of chrome plating onto variety of substrates

Hello! We plate hard chrome coatings onto a variety of cylindrical substrates (steel, copper, nickel). I am trying to find the most accurate and non-destructive method of measuring coating thickness on these substrates.
One method being used now is measuring diameters before and after plating with an Outside Micrometer (half-moon shaped micrometer). This method can provide a high variation in results depending on technique by measurer to determine that s/he is at the center (diameter) of cylinder.

Is a different method needed for each substrate?

I have used Eddy current gages in other applications (not for chrome on cylinders, but for flat parts) and XRF - but cannot use XRF for this application due to the dimension of the parts.

Please advise!

Allison Vaughan
Process Engineer - Plater - Chester, Virginia
June 2, 2011

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June 16, 2011

Hi Allison,

I'm sorry I don't exactly have an answer to your question as I have my own in. Just trying to gain a little additional information and maybe elicit someone interested in helping us.

From what my (office of Materials Tech.) told me the XRF's need to be at least 4KW to be able to measure chrome thickness and of course the WDXRF's to be more accurate than the ED's. That office is acquiring an WD and I'm looking to get a hand-held so maybe we can come up with some kind of correlation so that I can use it on the floor.

We also still measure the old fashioned way before and after chroming. But as you know you have to be in the exact same spot and there is a bit of operator/measurer feel.

So we'll see if we can get someone in the know on this.

Good luck
Regards,

Steven Olszowy
- Washington, DC

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Steve,

I imagine that if you have the appropriate plated (Cr/Nickel) standard, you should be able to use XRF on the parts. I have no experience with hand-held units - so I cannot speak for the accuracy of those units. You may be able to get a tech rep from someone like Eastern Applied to assist you.

What I learned from other sources (than this site) regarding my own situation is that the hand-held eddy current gauges should be pretty accurate for my application for Cr/steel and Cr/Cu but that if Ni is present between coatings, that the probe can provide false data.

I agree that Mic-ing the roll has too high of variation for me to trust it for precise measurement (my opinion anyway).
Good luck with your hunt for knowledge!

Allison Vaughan
- Chester, Virginia
June 20, 2011