Measuring thickness of nickel plating on nickel-bearing substrates (nickel-cobalt, stainless steel)

A. Dave: I was in the coating thickness measurement industry many years ago (approx. 1985-1990). The only other method I can think of (and I assume it's still in use) is coulometric, where a very small, defined area is deplated. The amount of time necessary to reach the substrate is, of course, proportional to its thickness. Standards are used to ensure accuracy. Drawback: it is a "destructive" test. The test areas can be fairly small (< 0.1").

The company I worked for, Twin City International, is OOB.

1st of two simultaneous responses --

A. You can make a cross-section of the sulphamate nickel coated Ni-Co alloy and measure the coating thickness using an optical microscope. Adequate measures should be taken while cutting the samples to prevent damage of the nickel coating. Electrodeposition of a thin layer of copper over the nickel coating could prevent damage during cutting.

2nd of two simultaneous responses --

A. I'm impressed you want to measure down to 7.62 µm - that means you need to measure to ± 5 nanometers. I do not know what you want to measure and why, but these are extremely small units and I am not convinced you actually need it. However, if you do, try using AFM microscopy, or possibly a betascope, but you will need to have a good substrate. Alternatively, try doing a bit of metallography and use an SEM - optical microscopy doesn't go down to the sub micron level!

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Thanks Trevor, but I happened to notice that if we convert Douglas' numbers to inches, his range comes out to an even .0003" to .0005". So it looks like the extreme precision of the 7.62 µm number was probably just an artifact from a conversion from inches to microns, rather than an actual requirement for that degree of precision. The conversion took us from one significant figure to 3 significant figures on a scale 2.54X as small, imposing a precision 254X as tight as probably intended :-)

So XRF or conventional cross-sectioning and optical microscopy is probably fine.

Readers may be interested in thread no. 7652, "Microsection vs. XRF method for plating thickness measurement".

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. NI CHECK ON STAINLESS STEEL PART: YOU CAN USE KOCOUR ELECTRONIC THICKNESS TESTER -- THIS TEST IS A DESTRUCTIVE TEST. OTHER EQUIPMENT IS FISCHERSCOPE mms SOLD BY FISCHER TECHNOLOGY. THIS TEST IS NON-DESTRUCTIVE.

A. I think ...
1. When you need to check the thickness of the nickel plating, you can use X-Ray Fluoressence (XRF); a well-known one is FISCHER SCOPE X-RAY to not destroy the surface.
2. When you need to check the deposit behavior, you can use cross-section cutting and magnifier analysis by Scanning electron microscope (SEM).
3. When you need to check the purity of the deposit metal (nickel), you can use X-Ray Diffraction (XRD).