Skip Copper Plating before Nickel-Chrome Plating?

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.

Mr Mooney,

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

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

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.

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,

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,

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,

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,