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"Preparing cross section for verifying plating thickness"

Current question and answers:

February 9, 2021

Q. Chrome plating to AMS2406 [affil. link to spec at Techstreet] .00020/.00050
Material is 440c
Outside lab is measuring plate thickness with a microscope in 5 places per ASTM B487 [affil. link to spec at Techstreet] and reporting each reading then averaging the 5 readings per the ASTM testing spec but is rejecting the job if a single reading drifts out of tolerance even though the specification instructs you to report the "average". I've talked to many "experts" and half tell me to use the average and the other half tell me to reject is a single reading is out. What is the consensus here relative to making the accept/reject decision based on an average.

Clark F Tracey
- Huntington Beach

adv.     u.s chrome

Previous closely related Q&A's starting in:


Q. Hello all,

I am working on a small project involving copper that is plated in tin. I have been tasked to find the thickness of the plating. Every time I try to cross cut the sample, I contaminate the copper and I am unable to see the plating thickness under the SEM. I am very new at this and would appreciate any assistance in methods of verifying the plating thickness.

Best Regards,

Chad Whetman
- Colorado Springs, Colorado


A. This is a perennial problem, but there is a method for this in ASTM Volume 02.05 [affil. link to spec at Techstreet] / ASTM B487 [affil. link to spec at Techstreet]. I don't have a copy, so can't refer but there might be guidance there.
You don't say if you are dealing with just copper on tin, or both on another substrate. Also how you are preparing the section is paramount. If just copper on tin, and depending on relative thicknesses, I would try cutting at an angle to increase the thickness of the coating and correct back for the angle.
Best of luck, and rather you than me.

Martin Rich
Ship Repair - Plymouth, UK


A. Chad,
Without knowing anything about the part you are cross sectioning, I can not suggest the right way to actually cut the sample. I have had the best luck using high carbide routing bits to cut samples. The polish you use for final polishing should be compatible with both copper and tin. DI water should also be used to wet your polishing wheel. Cross sectioning suppliers can be a big help to people new at the job. See if your supplier can send a tech to your plant to work with you for awhile. Hope this helps!

Mark Baker
Process Engineer - Syracuse, New York


A. You may have to plate the part in the lab with copper since the tin is so soft. I switched from bakelite mounts to epoxy mounts for plated parts.

James Watts
- Navarre, Florida


A. Depending on the dimensions of the part, and your target thickness for the tin layer, XRF may be your best bet. I don't have the specs for my XRF handy, but the tin layer would have to be fairly thin, most likely in the <0.5 mil range.

Jeff Marten
analytical - Colorado Springs, Colorado

April 8, 2011

Q. I work in a coatings company and we want to start doing our own cross sectioning to examine coating thicknesses. Looking for the right literature or classes for information on materials and techniques to use

Mike Cook
R&D Technician - Eden Valley, Minnesota, USA

April 11, 2011

A. I'd start by contacting the vendors of cross sectioning equipment.

James Totter
James Totter, CEF
- Tallahassee, Florida

April 15, 2011

thumbs up signThanks for the input Jim

Mike Cook
R&D Tech. - Eden Valley, Minnesota

April 18, 2011

A. Struers and Buehler have a lot of information available for download from their websites. Here is one example for preparation of zinc coatings:


Toby Padfield
Automotive component & module supplier - Michigan, USA

April 20, 2011

A. Try plating the tin with a harder metal such as nickel. The adhesion may not be brilliant, but it will do a job. Then cut your section, but at an angle. The trick is to cut the angle as far away from the vertical to your surface as possible, so cut it at a very shallow angle parallel to the surface. You should then polish the section and inspect it under a microscope.
The nickel will protect the tin and prevent it smearing and the amount of tin you see in your section will be related to the actual thickness by the cosine of the angle you have cut the section away from the vertical to the tin surface - simple schoolboy geometry!

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

April 24, 2013

Q. Hello dear,
I am studying carbon nanotube thin films. My problems is thickness measurement method; please help me to the way for measurement by SEM cross section.

Amir Zilaie
- Ahvaz, Khozestan, Iran

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