Copper plating of stainless steel screws

A. Hi, Tom. Something that most people may not realize is that electroplating is very much a jobshop oriented business. Even the biggest manufacturers, like the auto makers and appliance makers, have pulled out of the plating business and are relying upon jobshops for their plating. So you may be looking to find a plating shop to plate your screws rather than equipment to plate your screws in house.

Plating is very thin, usually measured in ten thousandths of an inch, rarely in thousandths, so it will not improve the conductivity of a screw by much (but it will improve the contact resistance). Is it possible that some brass alloy will give you sufficient strength and far more conductivity than stainless steel?

But, yes, the stainless steel screws can be copper plated. Plating of stainless steel usually starts with a Wood's Nickel Strike because the thing is, you can't successfully plate onto tarnish or a passive skin, you must plate on fresh, active metal -- and stainless steel passivates almost instantly. The nickel strike simultaneously dissolves the tarnish while it deposits a fresh layer of nickel plating. Good luck.

Q. We are looking to use these screws in a high voltage, high temperature environment. We need the strength of stainless steel, as these screws will be load-bearing. We also need the screws to be able to withstand high temperatures, which is why a copper screw, or even a brass screw will not work. We need the screw to be able to pass on RF in this application. We do not need to pass the current through the whole screw, we just need to have a skin on the screw to pass on the RF current. We were thinking of purchasing one of the "home electroplating" kits that we have heard about, but we are looking to plate small screws (5 mm), and will need a basket of some sort. Thank you for your help.

A. It's theoretically doable. It requires an alkaline cleaning step, an acid activation step, a Wood's nickel strike, and copper electroplating--with rinses between each process. You may want a post-dip in some kind of copper preservative like benzotriazole ⇦ this on eBay or Amazon [affil links] .

I'll express my opinion a 2nd time though, that you may wish to look for a plating service rather than plating equipment though. While a hobbyist may get away with simply buying and using a hobby plating kit, electroplating was our nation's first categorically regulated industry and a business will require discharge permits, regular sampling, effluent monitoring and reports, toxic waste manifesting, etc. Unfortunately, there is more to robust, reliable plating and its waste treatment than most people would think.

Good luck.

A. Hi, Alex. I don't think you are going to successfully plate copper directly onto stainless steel. Please investigate the subject of Wood's Nickel Strike; this is an almost universal step in plating onto stainless steel. Good luck!

Regards,

A. Hello, Reg. When you say "similar need" ...

There is nothing wrong with trying to electroplate for a school science project using copper pipe as the electrode, but if you are speaking of any sort of a functional product, as opposed to educational play, this is like fastening your automobile rims with lug nuts whittled from a stick.

We have an FAQ that covers science project copper plating, but functional plating is a fairly rigorous science; and trying to plate copper directly onto stainless steel with proper adhesion does not in general work. Nor does using low quality metal like copper pipe as the anode. Good luck.

Regards,

A. Try this procedure for copper plate per MIL-C-14550B, Class 3 (you can get this spec for free at the following: assist.daps.dla.mil/quicksearch/
then enter the MIL spec number in the Document ID. Different coating classes based on coating thickness. The spec is obsolete (now handled by ASME/AMS or something) but it is still good.

I don't know the particulars of each step unfortunately because I don't perform it, I just require it on my parts:

Solvent Clean
Glass Peen (150 micron or smaller grit)
Solvent Clean
Alkaline clean (Anodic)
Rinse
Acid Pickle to remove heat treat scale
Rinse
De-Passivate
Rinse
Copper Plate
Rinse
Copper Conversion (Dip)
Rinse
Dry

It's thin but it works on many stainless and alloy steels (omit acid pickle and de-passivating for alloy steels).

A. Don't know if it would help but stainless steel screws already copper plated are available from suppliers.

A. Hi, Abhiraj.

I appreciate Jeff Oakley's efforts to help us, and you can certainly follow his advice and see if it works. Personally, I don't think it will work reliably and robustly though. And glass peening may not be economically reasonable depending on the type of parts you are processing anyway.

Regards,

Q. Dear Sir

What are the factors responsible for plating?

What factors are taken into consideration in the electroplating?

How to calculate the plating time for acid copper?

Is there any formula for this?

Please help

Usually available on eBay;

sometimes on
AbeBooks or Amazon

(affil links)
free pdf is currently available from academia.edu

"Electroplating Engineering Handbook"
by Larry Durney

on AbeBooks

or eBay or

Amazon

(affil links)

A. Hello again Abhiraj.

Many metals, like copper, can be moved from the surface of one object to the surface of another by applying low voltage DC current to the two objects while they are immersed in a conductive medium. The metal oxidizes and ionizes from the positively charged object (the anode) and goes into solution; the ions migrate through solution to the negatively charged object (the cathode) where the excess of electrons reduces them back to metal. The "formula" regulating this is Faraday's Law, which is nothing complicated, just a way of saying that if you move a given number of electrons through the external wiring from one pole to the other, a proportional number of ionized atoms will move through the solution from one pole to the other. In other words, the amount of metal deposited is proportional to the current multiplied by the plating time. 96,485 amp-seconds will deposit one gram equivalent weight.

However, when you ask "what factors are taken into consideration", you are moving from a theoretical discussion that can be explained in a paragraph, to the practical and empirical knowledge that fills entire aisles of libraries and constitutes the acquired knowledge of a lifetime. That's a lot to ask :-)

For example, facts like you probably can't get sufficient adhesion onto stainless steel without special measures, and you can't easily get adhesion of nobler metals onto baser metals because the Nernst Equation factors can lead to immersion deposits. Please try to get access to a plating text like the Metal Finishing Guidebook.
or the Electroplating Engineering Handbook.
for an introduction to these factors. Although we can't answer open ended questions like that one, people can probably help if you are able to post more specific questions. Best of luck!

Regards,

A. Hi all,

I was taught this formula when calculating plating times and thicknesses.

Number of components x area /144 x current density = your amps.

Number of components x area x microns req'd x Factor / amps = time.

The optimum current density for acid copper is 10 amps per sq/foot and the factor to use is 0.175

I used this formula when I was working in the electronics plating industry, the optimum cd and the factor are different for each process and metal wishing to be deposited.

Hope this helps.

Russell

A. Try a copper cyanide strike onto stainless steel.

A. Hi Blaine. It's very unlikely to be satisfactory. The problem is that simple electroplating, moving metal from one electrode to the other as demonstrated in our FAQ and as you saw in school is easy, and fun and informative for kids to see, but it's like teaching kids "how to oilpaint". Sure, they can take a paintbrush and apply oilpaints to canvases, but their paintings won't contain much art ...

The metal you deposit will probably not be thick enough nor bright enough, and almost surely will rub right off for lack of adhesion. Unfortunately, moving metal from anode to cathode is very easy, but getting that metal to constitute a useful deposit is much more difficult. There's a lot involved in robust electroplating.

Regards,