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topic 56531

Method to identify tin plating versus nickel plating

Current question and answers:

January 22, 2021

Q. Spot check for testing for Sn on Al substrate?

Hi
Just wondering if there would be any simple lab check to test for the presence of tin on aluminium substrate,
We have use of an handheld XRF gun which is perfect, but after our tinned aluminium bus bar is housed we are unable to use this to do specific spot checks, is there a test which can be done that reacts with the tin to give i.e., a precipitate or colour change to show presence?

This would need to be a non destructive test if possible.

Thanks in advance for any response

Ryan McGrory
- Derry City, Ireland




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Defelsko Positector combo magnetic & eddy-current coating thickness tester

January 2021

A. Hi Ryan. Since you are very happy with XRF, but apparently can't get the gun into proper position is an assembled unit, I wonder if there is some sort of flexible extended probe either for XRF or beta backscatter which would allow you to reach the area. Another possibility would be to check whether you can reliably determine that tin is present with a hall-effect thickness tester?

I hope to be corrected if wrong, but it sounds to me like a non-destructive chemical reaction test is an oxymoron.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


January 26, 2021

A. Hi Ryan.
As Ted says, even a spot test is destructive. Probably you can try to use a small swab with a drop of Hydrochloric acid to pick up some Tin ions and after that put a drop of diluted Cacotheline (CAS Number:561-20-6, may be toxic) on the swab. It should give a purple colour with Tin ions. However, I'm not sure if (and how) it reacts if Aluminum is present. (Don't forget to rinse a spot that was touched with acid).
If you try it - please let us know how it works. Good luck.

Leon Gusak
- Winnipeg, Canada




Previous closely related Q&A's starting in:

January 14, 2011

Q. I am a project engineer working on a proposal to switch electronic buss bar coating from tin plating to nickel plating in an attempt to improve thermal properties of the buss bar. Occasionally the folks requesting the change don't provide all details so unfortunately I don't have the plating specifications for either process. What I do know is that we are plating copper with tin and the result is a bright shiny surface. The same look will be sought in the nickel plating; I've been told that a visual comparison will be very subjective and may not be absolute.

Is there a non-destructive method or tool (visual, electronic, magnetic, chemical, taste test) to immediately determine if the buss bars are plated in tin or nickel? The tin and nickel plated buss bars are both shiny reflective surfaces.

Victor Serrano
Project Engineer - Buffalo Grove, Illinois, USA


January 21, 2011

A. The only non destructive methods I can personally think of require either EDX or a very high powered microscope. If you do happen to have a very high powered scope knocking around (able to see on the micron scale). I assume you don't have EDX or you would have used it. If you do have something like an SEM microscope around you can look for the formation of tin nodules/whiskers on the tin.

I seem to vaguely remember a chemical test you can use as well involving lye water, which will react with tin.

Mark McKinnon
- Rugby, United Kingdom


January 24, 2011

A. Victor,

If you have access to X-Ray Diffraction (often called XRD) this will readily identify tin from nickel. These can be tabletop machines or hand-held portable units.

If you have access to EDX for SEM that will do the job as well.

Brian Terry
Aerospace - Yeovil, Somerset, UK


January 24, 2011

There is a very easy spot test for nickel. Put a drop of 1% dimethylglyoxime and a drop of 10% ammonium hydroxide on the plated surface. If it is nickel, it turns pink. Quick, easy, and inexpensive.

Jon Barrows
Jon Barrows, MSF, EHSSC
Independence, Missouri



February 8, 2012

A. I am not an engineer, but I have heard that a cotton swab soaked with Scrubbing Bubbles bathroom cleaner will turn a color (pink?) if contacted with nickel. According to the MSD sheet, available on-line, it contains N-alkyl dimethyl benzyl ammonium chlorides.

Martin Richardson
- Westerville, Ohio, USA

----
Ed. note: "You don't need a weatherman to know which way the wind blows" -- Bob Dylan, "Subterranean Homesick Blues"


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