Metal finishing Q&As since 1989

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Copper vs. brass flash on steel wire clips, before nickel plating?

March 1, 2010

We purchase a small steel wire clip, which we have used for 30+ years in production of hand tools. The part is bent slightly, to take up manufacturing tolerances, at final assembly of our products.

Recently, we've had a problem with the nickel plating flaking off, when bent. Investigation has shown that the supplier's plating subcontractor used a brass flash, prior to the nickel plating. The parts were stripped, reflashed with copper, then replated. The parts no longer flake.

I've always thought a copper flash was the standard. Our supplier is saying that the plater did nothing wrong, that either copper or brass were acceptable, unless we specify.

Your thoughts?

Hyok Lee
Engineering Manager - Corona, California

Hi, Hyok. Not only would either be acceptable, but plating the nickel directly on the steel would be acceptable as well. I think what is needed here is a specification for a "bend test" or "mandrel test" whereby the plating shop certifies that the part can be wrapped around a mandrel of so-and-so diameter without flaking.

Many plating shops are knowledgeable and can help you write a specification, but ultimately it's your job to specify what you need.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 2, 2010

Thanks for the reply. Are you saying that nickel plating over brass flash, copper flash, and bare steel would all have equal adhesion, or are you saying that because we did not specify how the nickel plating should be applied, the plater is free to choose?

Hyok Lee
Garden Tools - Corona, California, USA
March 3, 2010

Hi, Hyok. If you don't specify what you want, they are forced to choose what to give you :-)

So they give you what bests suits their interpretation of the situation. If I was supplying the need, I'd probably do only nickel on the presumption that copper or brass could cause you some sort of problem under some circumstance, and wasn't specified. As for adhesion, again, the parts should be bent around a mandrel to demonstrate adhesion but it's hard to say that an undefined process that includes copper plating would inherently offer more or less adhesion than a brass plating or direct nickel plating process. The problem appears to be that the nickel flakes off, not that there is brass on the part rather than the copper you expected. And that probably has more to do with the nickel being different than the switch from copper to brass. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 3, 2010

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Hyok, It is important that you know and understand the criteria to which you work. It is possible to plate nickel directly on to steel, as it is also possible to plate nickel onto either brass or copper interfaces. My personal choice would be the use copper as an interface, because it is easier to control than brass plating; copper plating will also allow you to smooth out any imperfections in the steel surface. I would use a cyanide copper.
You will also need to specify the ductility of the nickel you are putting down, because if you have a low ductility, the nickel will break away from any substrate and cause failure. Ductility can also be related to hardness, so you need to consider your preferred hardness and the type of solution you are using for your nickel, as this too can affect the hardness and ductility. Just to add a bit more confusion - you will need to consider what stress in the nickel that you can tolerate; this too will be affected by your solution chemistry

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
March 6, 2010