How to do copper plating

A. Hello, Lapo. If you (or a reader) wish to demo copper plating for a school science project, we have an FAQ: How Electroplating Works, that will give you easy instructions for the project.

But sorry, your approach won't work for functional electroplating applications because copper is more "noble" than iron and will (as you saw) deposit on steel or cast iron without any current applied. This is called an "immersion deposit" and it usually has virtually no adhesion. Still, make sure that your component is absolutely clean (waterbreak-free) and that current is applied to the part before & while it goes into the plating tank ("hot entry") because that will help a little towards discouraging immersion plating.

The preplate cleaning should consist of caustic cleaning (detergent and NaOH) followed by an acid dip (HCl). But for onesy-twosy work you can scrub the part with a tampico brush and powdered pumice [on eBay or Amazon] as an alternate to caustic cleaning, and use a diluted HCl for activation.

For functional copper plating on steel you need to either electroplate an initial layer from a nickel strike bath, or from a copper cyanide (very dangerous poison) bath before you will be able to use the copper sulphate bath; these will not immersion deposit. You probably will be best off with proprietary additives (brighteners) to get good, bright, plating.

Electroplating involves working with hazardous chemicals, so it may not be an ideal casual hobby. If your desire is simply to get copper plating on the parts, as opposed to doing copper plating as a hobby and learning experience, plating is a jobshop industry and there should be a commercial plating shop available in your area. Good luck!

A. It is not something you would let children do without supervision, and some people might not find it impressive, but I did find a way to plate coins with copper metal. If you insist on trying to plate outside of an industrial environment, at least you won't be using concentrated acids, metal salts, and etc.

I tried to find a way to do this using only nontoxic chemicals (aside from the copper itself), but I needed to use some ethylene glycol. This stuff is toxic, has a sweet taste (or so I am told), and pets and children might be tempted to taste it, so it must be handled by adults and stored in locked cabinets. On the other hand, anything containing copper is not good to drink, and there is enough salt in this solution to act as an emetic.

All of these tests should be done under adult supervision, and the learning experience is bound to be better this way. Depending on the age of the witnesses, you can cover all sorts of exciting things, from cleaning coins with toothpaste to chemical calculations of normality and concentration to electrochemical equivalents. Except for the brightening agent, all other supplies are household items. The ethylene glycol should be stored in childproof areas, and the test solution should be dumped at the end of any experiment. All containers should be labeled, even as you are using them, as a matter of normal laboratory practice.

The solution described is low in the concentration of copper, as far as plating solutions go. If all of my electrolysis converted my copper anode to copper ions, and all of it ended up in the sewer we are talking about:

e =i x r
1.5 =i x 15 ohms
i x 15 = 1.5
i = 0.1 amps

If you run the cell for 2 hours, that's 0.2 ampere hours. Looking up cupric ion, we see that we deposit/dissolve 1.19 grams of copper metal per ampere hour. So the most we could dump down the drain is 0.24 grams, not an ecological nightmare. The final concentration of the cell of 100 cc, after 1 hour of electrolysis, could reach 2.4 grams/liter (this is unlikely, as gassing is very evident, indicating that we are not operating at 100% efficiency).

• 1. Strip the insulation from about 2 feet of copper wire. Clean with toothpaste, Multiscrub, etc. and a sponge or a soft bristle brush. Wear rubber rubber glovesrubber gloves [on eBay or Amazon] so you don't recontaminate the wire with oil from your fingers. Coil this up except for a few inches and place in a 150 cc [beakers on eBay or Amazon].
• 2. Add 100 cc of white vinegar [in bulk on eBay or Amazon], and 1 heaping teaspoon of Kosher salt, and 3-6 cc of ethylene glycol (depending on if it has been diluted).
• 3. Use a nickel, dime or quarter for a cathode. The shinier the surface; the brighter the resulting deposit. Clean as for the copper wire in (1) above.
• 4. Rig a 1.5 volt battery with a 30 to 200 (approximate) ohm resistor in series. Attach the positive terminal to the anode (the copper wire), and the negative terminal to the cathode (the coin).
• 5. Electrolyze this solution for 10 minutes or so. It seems to take a few minutes for some of the copper metal to dissolve and be available for plating. After this you can try plating some new coins. Clean the coins beforehand using an old toothbrush and some toothpaste, rinsing the coins with water (Wear gloves). You will have to look around for alligator clips or locking forceps to make some reasonable connection.
• 6. A copper color should develop after a few seconds of plating. Jiggle the cathode during plating. The plating brightness seems to improve after the bath has been electrolyzed for 20 - 30 minutes.
• 7. You can also plate pieces for longer periods. the deposit turns black during plating of more than a few seconds, but you can polish this deposit to an antique copper finish using toothpaste. The plating is attractive, but you can imagine that it is not as impressive or immediate in visual impact as plating gold onto nickel.
• 8. I had excellent success with adhesion on coins; all of my coins are now copper colored, and I suppose I will have to use them in automatic vending machines unless I want to explain what happened to them. I can't remove the copper with vigorous scrubbing. Just another reason why this process should not be left to children, unless you want all of your conductive trinkets in antique copper. (You DIDN'T let the children plate the tennis bracelet Aunt Constance left me … did you?)
• 9. This solution will copper (verb) iron nails by immersion. The smoother and shinier the iron, the better the copper immersion deposit.
  I did not get good adhesion when I tried to electroplate an iron nail; you would need a strike solution, and this would be difficult to make from household chemicals.
• 10. Immediately after testing, dump contents into the drain, and wash all equipment with water and detergent, then rinse with tap water.

Thanks for the kind words, Eamon. I believe that standard automotive anti-freeze is basically ethylene glycol, although it contains some corrosion inhibitors, but check the label. Yes, you are correct that Tom has described a plating process that does not require copper sulphate.

FOR Nikolas

MIX 1 TO 3, PRE THINNED VARNISH WITH COPPER POWDER, ATTACHING WIRE TO OBJECT AND COATING WIRE END UP INSULATION ABOUT 1/4 INCH. LIGHTLY DUST WITH SAME POWDER. THEN PLATE AS NORMAL (ALLOWING VARNISH TO DRY 12 HOURS.--WORKS FOR ME 1 PART-POWDER/3 PARTS TH.VARNISH).

It may be against Federal law to use root killer in a way not in accordance with the indications for use as a root killer. Does anyone know what this stuff is, chemically?

Proprietary products rarely tell you what they are 100%, because then everyone could copy them and claim them to be identical and all their development and marketing efforts wasted, but most root killer is essentially copper sulphate pentahydrate. Yes, there may be some contaminants that could be non-ideal for plating applications. Be beware that some root killers like RootX are NOT copper sulphate.

The composition of K77 root Killer is > 99% Copper sulphate. Here is the Cornell University site for the Material Safety Data Sheet: http://msds.pdc.cornell.edu/msds/msdsdod/a246/m122546.htm#Section2

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Ed. note: Thanks, Robert. Sorry readers, that domain name no longer works.

A. Hi, Michael. The purpose of the copper plating (in this case) is to be soft and buffable; most people probably consider "show chrome" to mean highly buffed copper plating under the nickel. But if you are not planning to buff the copper to a mirror shine, I think you'd be better off leaving out the copper plating, and just starting directly with nickel -- that's what most OEMs have done for many years now.

Electroplating shops do not make their copper plating processes from root killer, although they use a great deal of copper sulphate and thus have the potential for saving a lot. If you want to do better work than they, I can't really see using root killer, but only very pure products.

Try to borrow or buy a cheap copy of the Metal Finishing Guidebook or the Canning Handbook to see the principal differences between professional acid copper plating solutions and root killer, and to what extent they are or aren't important to you in your particular situation.

Good luck!

Thanks for your input, Kellin. About 1300 people visit this thread every month, so your contribution will certainly be appreciated!

You could be right that Lapo isn't the beginner he claims to be. But please remember that internet forums are giant one-room schoolhouses, read by 3rd graders and post-doctorates alike, so when someone labels their question as coming from "an absolute beginner", less experienced readers will certainly be expected to be addressed at that level, and need to be warned about things like the hazards of cyanide plating. Dozens of trained professionals have died working with it, including 6 at Bastion Plating in 1984, and a man in my very own town died a few years ago doing cyanide copper plating on his kitchen table, also putting the first-responding police officer in the hospital.

K-77 may well be a root killer that is 99%+ copper sulphate as you say, but you've illustrated the hazard of the procedure perfectly because if others instead select RootX, for example, they get a herbicide with NO copper sulphate.

An "absolute beginner" may not realize that jobshop plating services are readily available, so I advised of that option as well because being "a little put off" can cut both ways:
Many people love boat maintenance, for example, and are happy as a clam spending the day with a beer in one hand and a scraper in the other -- but I'd rather be in a dentist chair. I repeatedly ask on boating sites where I can get so-and-so fixed, only to have people thinking they are doing me a big favor by insisting that I can do it myself instead of answering my question :-)

You may enjoy hobby plating, but others can't stand it, and may appreciate learning that they can get it done rather than having to do it themselves :-)

Ad-hominem postings are distracting, time-consuming, and dilute the useful content of a site -- so please continue to offer advice and contradict any statements you disagree with, but please don't derail the discussion by criticizing myself or other posters. Thanks again.

A. Sorry, but a single potato battery will not suffice, Scott -- although a half-dozen hooked up 3 x 2 or 2 x 3 in series-parallel might!

Any copper sulphate you add will be to the good; it's not critical. So I'd say add enough to give a light to medium blue color. Good luck.

February 21, 2008

A. See our FAQ on How Electroplating Works for the details for super-safe copper plating for school projects, Dalton -- you can tell your mom that no chemicals except vinegar are used.

As for something different: have you ever decorated easter eggs by writing on the eggs with a white wax crayon or otherwise masking areas before dyeing to keep that area from absorbing dye? Maybe you can clean up a quarter real well, then make symbols with very thin strips of tape or nail polish before copper plating it? Electroplating often involves masking like that.

Best of luck.

A. Hi, Khaled. This thread has grown long and rambling, so although you say you've done everything we've talked about, I'm not clear what metal you are trying to apply to what substrate from what kind of solution :-)

But to re-state it from the beginning, you cannot electroplate copper directly onto steel with good adhesion from a copper sulphate solution. Is that what you were trying to do?

Regards,

A. Hi, Nathanael. Modern lead-free pewter is 90+% tin, and tin is anodic to copper. That means copper sulphate tends to auto-deposit on pewter as a non-adherent immersion coating just as it auto-deposits on steel. You probably need cyanide copper plating (very dangerous) or a proprietary copper pyrophosphate solution (available from EPI / Electrochemical Products Inc. [a finishing.com supporting advertiser] or Zinex). It is possible that hobby plating vendors offer proprietary copper pyrophosphate plating baths too. Good luck.

Regards,

A. Hi, Teresa

The anode and the cathode are the two electrodes. The electrolyte is whatever liquid you put them in. Hopefully you know what temperature is in terms of physical chemistry: it's movement or vibration of the atoms, so higher temperatures are going to aid ion mobility and result in faster electroplating. Whether it's "better" electroplating will depend on a lot of other factors, and I would guess that you are supposed to conduct an experiment to see the result. Good luck.

Regards,

A. Hi, Justin. Gasoline chemistry can be complex and I don't know if copper plating is compatible with gasoline. Plating blind inside a gas tank is exceptionally difficult for an experienced professional; the plating will only go where the electricity goes, and the electricity follows the path of least resistance (the shortest route). so I think you should do quite a bit practice with a less critical item before risking this item that you've worked hard on.

I think if I were you I would test immersion plating from a dilute copper sulphate bath on some similar item and see if you can get enough adhesion. Immersion plating will deposit evenly even in the corners. Put in a fresh fuel filter just in case :-)

Regards,

A. Hi Jay. First, I think you need to determine whether this will be a worthy finish if you succeed. Presumably it's for indoor use, as it will have no corrosion resistance. Second, it may not look too good, as you might not be able to successfully lacquer a hot stove pipe. So please try a small item before fooling with an 8 foot long one.

The galvanizing will be removed by the pretreatment process, and you will be doing the copper plating onto steel. If you don't want to send the stove pipe to a plating shop for copper plating, you can try a pen plating / brush plating outfit, available from a hobby plating supplier. There's a good chance you'll find it a humbling experience, so I'd urge you to try a small item, or practice on scrap, not potentially ruin an important item. Good luck.

Regards,

A. Hi Canny. I liked Philip Camp's response about using copper powder mixed with thinned varnish.

Vinegar based plating is for students to learn a science lesson and is not intended, and won't work, for any practical application. Plating from copper sulphate on top of the copper powder and varnish will work better . . . but you're still talking about hobbyist plating which is mere millionths of an inch thick; it will wear off very quickly I'm afraid.

I'm no artist but the best approach may be to carefully mask the area, then apply the flux to only a tiny dot so there is no visible solder. With less precision, this is what plumbers do when they solder copper pipes, i.e., they are careful to only sand and flux as much as necessary for the joint, and let the un-sanded oxide serve as a mask. Good luck.

Regards,