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topic 0713

Skip Copper Plating before Nickel-Chrome Plating?



1997

Q. Hello,

In chrome plating bumpers, is there a difference with respect to appearance and/or corrosion resistance (in winter conditions) between the two following processes?

1) dull nickel, bright nickel, chrome

2) copper, dull nickel, bright nickel, chrome

If there is a difference, can the options be made equivalent by modifying the duration of the steps?

Patrick Turcotte
MultiPro - Canada


1997

A. There are still some people who believe that copper offers a better appearance for the best "show chrome".

I was at one O.E.M. bumper plating shop about 5 or 6 years ago that was still using copper for one automobile brand. But I've been to many others, before and since, and I think copper is a rarity for O.E.M.s these days. It's pretty much restricted to antique and show car enthusiasts.

Further, neither the MFSA quality guides (www.nasf.org), nor anything else I've stumbled on over the years, claims better corrosion resistance performance for copper.

I think the story is like this:

There was once a time, before bright self-leveling nickel, that copper was important because the bumpers would be copper plated, then buffed, before nickel and chrome plating. When self-leveling bright nickel became available, many shops still stuck with copper--not only out of familiarity, but because it allowed them to deal with old work per the old specs, and it allowed continued buffing of copper plate, which could be an easier way of dealing with minor scratches when refurbishing old bumpers than repolishing the stock. So copper plating stuck for much longer than the O.E.M. technology really required. But I wasn't elected keeper of the oral tradition, so if someone thinks I'm wrong, please speak up.

In terms of corrosion resistance, it seems that having the proper activity ratio between the bright and semi-bright nickel, so that pits grow laterally instead of penetrating, is the key. This is controlled with the STEP test. To improve corrosion resistance, some wheel platers do electroless nickel before the duplex nickel and chrome, but I'm personally not aware of any bumper platers that do it.

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


1997

thumbs up sign Mr Mooney,

Thank you very much for your response, your insight is quite appreciated.

Patrick Turcotte
MultiPro - Canada


1997

A. I think Ted is right, copper is out. Double layer nickel gives a bright and ductile deposit. Sara

sara michaeli
Sara Michaeli sara michaeli signature
chemical process supplier
Tel-Aviv, Israel




Q. While I think that copper is out, for the most part, on O.E.M. bumper plating, let me ask about aluminum wheels. I read that some quality wheel manufacturers are zincating and electroless nickel plating, then acid copper plating, baking, buffing, and nickel-chrome plating. My question would be why the copper plating? Per an article I read, it's for buffability. So my question would be, can you just duplex nickel plate the electroless nickel, or will it be too dull? -- or have some other undesirable characteristic?

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


1998

Q. I am a plater in a small job shop. We use a cyanide copper strike prior to bright nickel, chrome plate. In all the years I have found that the copper does help on corrosion resistance on plated parts in weather conditions. One thing I found is on any kind of exhaust pipe, (where heat is high), I skip the copper and go direct into bright nickel. I have never had the problem of blistering since I have practiced this process.

Does anyone have any pro's or con's on this?

Jim Coughlin


1997

A. We plate approximately 3000 O.E.M. Bumpers/day

I remember having many arguments with our long time managers over appearance of copper plated bumpers. They claimed that appearance-wise the copper added depth to the plate and used a simple reflectivity test of standing a ruler up against the bumper and seeing how far you could read its reflection. The results were in coppers favor but so slightly that it made little difference. Only the copper buffing helped to fill in any polishing lines.

If the steel is of good quality, flat polished properly and then polished and buffed before plate thoroughly you will wind up with the same results.

Corrosion wise a good STEP is the most important. Also a High sulfur barrier nickel is used between the semi and bright that helps considerably. Some platers tried putting a thin noble nickel layer over the bright (basically they ran their microporous nickel without any powder) which did affect corrosion sites but no one pursued this that I know of.

Mark Boscariol
plating shop - Toronto, Canada



April 2, 2012

Q. HI
WE WANT MIRROR FINISH ON OUR PRODUCTS (WE ARE USING CRC SHEET) WITHOUT BUFFING, TO BE ECONOMICAL. PLEASE SUGGEST THE RIGHT PROCESS.
CURRENTLY WE ARE DOING BUFFING AND CLEANING LINE AND THEN NICKEL. BUT STILL AFTER GIVING HALF AN HOUR IN NI BATH WE ARE NOT SATISFIED WITH QUALITY. LONING MARKS ARE STILL THERE.
WE ARE USING COPPER WIRE RATHER THAN JIGS.
LOOKING FORWARD FOR A POSITIVE REPLY.
REGARDS

ABHISHEK GOEL
METAL INDUSTRY - LUDHIANA, PUNJAB, INDIA


April 5, 2012

A. Hi Abhishek.

Are you using proprietary nickel plating processes? If not, what are you using as a leveler? This sounds like just a single layer of bright nickel. I think you'd probably get a better product from a self-leveling semibright nickel plating process followed by bright nickel.

I don't think the copper wire in lieu of jigs is relevant to this problem though (assuming the wire is heavy enough to carry the current. Good luck.

Regards,

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



Decorative Chrome plating without Nickel or White Bronze?

July 9, 2014

Q. We are purchasing Pen parts, made of brass which are then electroplated. The parts are Copper plated (0.4 micron) and then Chrome plated (0.22 micron - Hexavalent free Chrome plating). We want the parts to be Nickel free - without the Nickel plating layer that is usually added between the Copper and Chrome.

The parts need to pass a 24 hour corrosion test (ISO 9227 [affil. link to spec at Techstreet]) and a 16 hour artificial perspiration test (Avon Test APJTM 62.303-1/1981).
So far, plating companies are advising us, that without a Nickel plating layer or a White Bronze plating layer, the parts will not pass the required corrosion and perspiration test. Samples tested so far, verify this claim.

From what I was reading, it seems that micro cracks in the Chrome layer seem to be a contributing factor for failing the test (and of course the missing Nickel layer). Further reading suggests, that "thin dense Chrome plating" reduces or even eliminates the micro cracks. I have the following questions to the forum:

1. Will an increase of the Chrome plating thickness, provide a solution, and if so, what would the plating thickness need to be?

2. Will a dense 0.22 micron Chrome plating improve or eliminate the corrosion issue?

3. I was also reading that the plating preparation and quality of the plating can be a contributing factory for corrosion. Can a brass part with 0.4 micron Cu plating and 0.22 micron Cr plating, if plated in good quality, pass in general the two tests?

We are also considering to add an Electrophoretic (E-Coating) top lacquer. However, the appearance of the Chrome colour will change and will have a slight yellow tint, which we want to avoid.

Any other thoughts or recommendations on how to have a Chrome finishing of the brass parts, which can pass the corrosion and perspiration tests, without using a Nickel plated layer (and any other layer like White Bronze - we would only use Cu and Cr), are appreciated!

Best regards,
Troy

Troy Fleur
Purchasing - Hong Kong


A. Hi Troy. Thin Dense Chrome is a proprietary name and process which we cannot comment on (why?).

But I am surprised that you are finding the appearance of chrome plating directly on copper satisfactory. Although I have not seen this, I would not have expected it to be nearly as bright and shiny. Unfortunately, as you've discovered, copper plating does not offer the kind of corrosion resistance you seek, nor does chrome. Although copper is often hard chrome plated (a heavy layer), I've never personally heard of a thin layer of chrome directly on copper ... you may be going it alone with this approach. If there is some reason you want to do this besides cost reduction please let us know.

Luck & Regards,

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



Decorative chrome finishing on SS without copper layer

October 30, 2020

Q. We are setting up a plating line for decorative chrome plating on 201 and 300 series SS (may do 400 series as well if required by the customer).

Initially we were advised with performing acid cu layer for good brightness/high reflectivity and then bright Ni.
However it is recommended that if the SS was polished well to begin with, we could do without the Cu layer and from Wood's nickel complete with bright nickel and Cr.

We have more or less thought of the following:
soak clean, electropolishing (to take care of e-clean AND mechanical polishing), Wood's Ni, bright Ni, Cr.

Is this a good process solution?

ibrahim ismail
- Cairo egypt


October 2020

A. Hi Ibrahim. Although it is probably safe to omit the copper layer, I think you should think twice and carefully study your idea of electropolishing and how it fits or fails to fit into your process sequence --

• Although electropolishing is very good at removing asperities for a smooth finish, it is far less effective at converting a wavy surface to a smooth one. Depending on what you are plating you might not be able to proceed directly to electropolishing without mechanical preparation.
• Electropolishing might be able to replace the nickel-chrome plating rather than the polishing in some cases on some substrates. Our learned colleague Jeffrey Holmes advises us a couple of times on this site that the appearance of electropolished stainless steel can be fully the equal of chrome plating in some cases.
• Perhaps electropolishing can obviate the need for electrocleaning, assuming a good soak clean, but it is a very effective passivation procedure which is the opposite of what you want the Wood's Nickel to do -- so I'm not sure it actually delivers any benefit in your cycle.

Keep us posted on your findings and trials.

Luck & Regards,

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


October 30, 2020

Q. Dear Ted,

Thanks for sharing the info.

With the little exposure we have to metal finishing, I agree with you that SS can be polished to a high shine....however the inherent colour of polished SS seems to be an acquired taste as opposed to NiCr's hue and luster (at least in the specific market we hope to cater to).

I was unaware that electropolishing lends to passivation in-process. I was under the impression that passivation would happen once the surface is stripped off its outmost layer and then intentionally passivated or allowed to oxidize/passivate naturally thereafter. Can you please elaborate further?

Also, are there varying degrees of how passivated SS can get? I mean wouldn't the degree of passivation of an SS sheet that came directly from the steel mill be the same level of passivation that would occur (according to your advice) if we were to electropolish...that would in turn make Woods Nickel less effective?

Eagerly looking forward to hearing from you and your other colleagues. Many thanks in advance!

Ibrahim Ismail [returning]
- Cairo, EGYPT


October 2020

A. Hi. Yes, to some extent some materials can sometimes become passivated through age. But in the case of stainless steel, passivation is an engineered process to remove iron and grow a chrome oxide skin to try to keep iron off the surface. Whether passivation is done by immersion in strong nitric acid, or by electropolishing (oxidation in a strong acid), the result is a sound passive skin. I am not saying that Wood's Nickel is incapable of reliably removing it (it probably can do so), just that electropolishing is a step backwards from the active surface required if the intent is to nickel-chrome plate.

Luck & Regards,

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

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