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Non-cyanide copper plating thickness limit
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What is the practical upper thickness limit for a functional copper plating on mild steel using a non-cyanide process?
Kirk Cooper- Sidney, Ohio
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Hi, Kirk. Copper electroforms have been built at least 1/4" thick. So the answer is that there is probably no practical upper thickness limit to copper plating. If you can phrase the question in terms of the details of your own situation maybe we can help further. Good luck!
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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Ted is correct. The question is so broad. When you say non-cyanide, you open the door to several chemistries (sulphate, pyrophosphate, fluoborate). Of those, the one most used to develop thick plates is the sulphate. A practical limit could be how much roughness can be tolerated on the outer surface. Without additives, which tend to increase stress and can lead to cracks, thus limiting thickness, 1/8" can be done with no more roughness than a piece of coarse emery paper. Beyond that, you can go up and end with something that resembles a coral or a sponge.
Guillermo MarrufoMonterrey, NL, Mexico
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The key to my question is non-cyanide plating. For a commercial plater, plating a steel part which will be torch-brazed, what is the thickest copper plate you would feel comfortable putting on using a non-cyanide process?
Kirk Cooper- Sidney, Ohio
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You're still not quite telling us what you are trying to do, Kirk, but continuing to cast the question in the abstract where I can't say anything without a dozen ifs ands and buts :-)
We don't know if we can start with copper pyrophosphate and finish with bright acid copper, nor whether we can buff in mid-process to smooth it back up. Are we wasting time debating whether we can get to 1/4" or only 1/8" when you would be satisfied if you can reach 10% of that?
An often used approach is to nickel plate first, then you can directly plate a simple copper sulphate solution very thick. Is a nickel strike objectionable in your application?
We don't know why it's supposed to be cyanide-free--whether a cyanide strike is forbidden on ecological or safety principles, or it's perfectly acceptable, but you want the large grain structure of a non-cyanide as the final plate. We don't know if the copper is supposed to be bright for decorative purpose, whether it needs to be a good wear surface, survive a carburizing heat treatment, etc.
I guess I'm saying that I wish your inquiry would start: "Here's what I am trying to do: ..." :-)
Good luck and thanks.
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Ted Mooney, P.E. finishing.com Brick, New Jersey |
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OK - I consider myself sufficiently chastised for lack of detail :-) Here's what I am trying to accomplish: copper plate a mild steel part which will later be brazed to another part. For environmental and process flexibility reasons, I desire to minimize or eliminate use of cyanide in the strike or the plating bath. Desired plating thickness ranges up to 0.002". Aesthetic function of the plating is secondary, but it should have a surface finish (Ra) not exceeding 0.0005". Brightness is not critical, but consistency of appearance is. Hardness should be similar to that of a cyanide-based process. Thank you.
Kirk Cooper- Sidney, Ohio
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Thanks, Kirk. You may already realize that acid copper cannot be deposited directly onto steel surfaces because it will "immersion deposit" and offer virtually no adhesion (it won't survive brazing). If you can't use a cyanide strike, you would need to try either a pyrophosphate copper strike or a nickel strike.
Then you can finish with an acid copper (sulphate or fluoborate). I don't think .002" is a technological hurdle as, when I was involved in the stripping of the copper from the William Penn city hall tower in Philly, we discovered that they had plated copper 20 times that thick a hundred years ago.
It may be possible to directly plate .002" of a proprietary pyrophosphate copper in a single step, but I don't know enough about that to comment; you could inquire of a supplier of that process like EPI. Best of luck with it!
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |