is there an easy identification test for Nickel and Chromium ?

I have a small table on a watchmaker's jewelling press.

... The shiny plating is bubbling and peeling

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.... Please excuse the ‘moody’ lighting

Horological tools are commonly Nickel plated, but this looks [perhaps] more like Chromium plate.

I would be interested to know which it is; but have not yet found a simple, economical, test for either or both metals.

Can anyone advise, please ?

MichaelG.

If there are flakes that you can pick off try one for magnetism. That said I'm not sure that chromiu isn't magnetic, just that nickel is.

Without giving it much consideration I would think that nickel will have green(ish) colours, in solution, whereas Chromium will also have a blue colour in one oxidation state.

Looking up oxidation states of them may provide some insight.

Chrome plating is much harder than nickel plating and usually much brighter. Compare a few items that are chrome plated using a fine steel scribe. Do not press hard and try to scratch the surface. The difference between that and normal steel and nickel is striking. Do not press hard because the plating is thin and if you press hard then the metal underneath will deform and it may appear scratched, Practice on a few chrome plate items and mild steel to see the difference.

I would be surprised if it was chrome plated. Nickel has a slightly off silver colour towards cream or yellow. Chrome would be a cold neutral grey. An alternative called tin-nickel has been used on certain scientific instruments, like nickel in colour but less creamy yellow.

Edited By old mart on 26/11/2020 14:20:45

Digressing slightly from the thread but still staying with chromium plating could someone with metallurgy knowledge explain what causes the micro bubbles in chrome plating that often appears on brass items that are chrome plated, for instance plumbing items such as taps. I have a good quality mixer tap fitted to our kitchen sink, it’s actually a Brita filter tap, and the top of the tap has these small pimples or bubbles that have appeared on the top surface of the tap. I assume that the brass work of the tap is plated with perhaps nickel or copper to key the chrome plating so is it a reaction to the substrate? I have tried to photograph the “bubbles” but not successfully as yet, apologies to Michael for sidetracking his thread.
Dave W

I think that “bubbling” is caused by bad adherence of the plating. But what is then in the bubbles underneath?

Off topic. At university our professor of metallurgical thermodynamics told us the following.

If you take a cast iron pan (for cooking) with email on the outside only and you fill it with sulphuric acid then after some time the email on the outside delaminates. This is caused by hydrogen diffusing through iron and not through email. Therefore, the pan should also have email on the inside, if you want to cook in sulphuric acid .

Edited By Jouke van der Veen on 26/11/2020 15:22:56

Thanks for the responses so far

To my eye, the plate looks a little more like Chrome than Nickel [and I have seen a lot of both] ... which was the reason for my question.

It appears to be plated direct onto the Brass surface ... which probably explains the problem.

I have not yet looked under the bubbling, but will be removing some samples of the ‘foil’ for inspection.

Ultimately, I may wish to strip it all from this component ... which is why I feel the need to know what it is.

MichaelG.

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Not really a sidetrack, Dave ... you’re welcome

I suspect that the quality [or absence] of the under-plating might be the cause of both our problems.

MichaelG.

Thanks Michael, seems feasible but not what you expect from a premium product, then who sets the standards of a premium product. Dave W

A brief update ...

I peeled a strip of the plating from the Brass and have confirmed that it is slightly magnetic.

More anon

MichaelG.

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P.S. ___ Still doing my homework, but when I have more facts,  I may try asking Mr Baker:

https://www.bakereng.co.uk/electroplating/nickel-plating/

Edited By Michael Gilligan on 26/11/2020 19:55:09

In the old day (ha ha) it went steel>copper flash>nickel1>nickel2>chrome. Chromium at ecenomic plating thickness is water porous so the water is heading for the steel. The two layers of nickel are put on under different regimes so do not have the same electropotential. This makes the water attack along the outer layer leaving the inner layer to protect the steel and stave off rusting until the warranty is over. Of course the side effect is your shiny chrome is undermined and flakes off but that is after the warranty period too.

Should have said if not obvious that chrome offers no protection it is only there be shiny. All that stuff about oxide layers etc is to protect the shine, not the metal. Only the nickel protects but now they skimp on that putting on just enough to key the chrome to get the shine to get out the door.

Edited By Bazyle on 26/11/2020 20:35:41

Look online for jewellry testing kits! My Cuz got a gold testing kit delivered today, and the leaflet mentioned tests for chrome, nickel and platinum, so you might be able to get a small kit of chemicals to do the job!

Phil.

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Which is all fine, except that my item is

1. from those good old days
2. part of a good quality Swiss tool
3. plated on Brass

MichaelG.

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Thanks, Phil

I’m slightly surprised because, prior to starting this thread, I looked here: **LINK**

https://anchorcertanalytical.com/what-to-test-for-in-nickel

... and read “As Nickel testing is destructive, lengthy and expensive ... “

[probably serves me right for starting at the top]

MichaelG.

Michael

Nickel will readily come off with an electric current and a mild acid bath giving a green/blue solution (reverse of nickel plating). Just start the process to see if the surface suddenly brightens.Chrome will not come off in mild acid.

My experience from stripping chrome and nickel off old parts.

Norm

Edited By norm norton on 27/11/2020 15:10:41

Can I suggest.

With known sample of plated chrome and another of nickel

Arrange ref probe to dip in small drop of tap water with perhaps dash of baking soda. You need a electrolyte.

Drop of electrolyte on unknown measure voltage between sample and probe. Compare voltage between the two probes.

The lowest different will indicate the match......

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That makes sense, Norm

Do you foresee any risk to the brass ?

MichaelG.

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You certainly can, Jason

MichaelG.

When I was in plating, nickel was never removed electrolytically. A commercial stripping solution called Ni Plex was used. This was for nickel and decorative chrome on steel. I don't know about a brass base, though.

If the plating will peel off, it will be nickel, that thickness of chrome would not be ductile at all and would crack off.

Edited By old mart on 27/11/2020 19:33:41