Letter 064

Help to do copper electroplating

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I'm an absolute beginner in electroplating. I would like to copper some iron pieces (plate, pipe); so I've turned or filed to the desired dimension and shape. I've prepared a solution of copper sulfate [link is to product info at Amazon] CuSO₄ (~200 g/l) and H₂SO₄ (~5 g/l) in water (deionized). When I've used this solution with a copper wire as anode and with 10 mA/cm² as maximum, the result was very bad. A lot of copper has deposited on iron but rinsing it under water-tap the copper goes away. So I've reduced current density also to zero: if I put iron in the same solution the result is the same: a lot of copper badly attached on iron, and under the copper the iron was oxidized (dark color).

Further attempts (current density between 0 and 100 mA/cm²; no H₂SO₄ or more than 10 g/l; CuSO₄ from 50 g/l to 200 g/l) have produced the same result: I've also tried various polishing by inorganic (HCl, H₂SO₄, NaOH) and organic (tetrachloroethylene, turpentine, Acetone [link is to product info at Rockler] ) solvents. Temperature of bath has always been around 18 degrees Celsius. Only if I put iron pieces in the bath for few seconds and then rinse it, I can get a very very thin copper deposit (I was not able to measure it with .01 mm caliper) that's well attached to iron, but it's so thin that it isn't useful at all.

Where am I wrong? Many thanks in advance.  

Lapo Pieri

Hello, Lapo. If you wish to demo copper plating for a school science project, that's one thing, and we have an FAQ: How Electroplating Works, that will give you easy instructions for a school project.

But sorry, your approach won't work for 'real' electroplating applications because copper is more "noble" than iron and will therefore (as you saw) deposit on steel or cast iron without any current applied. This is called an "immersion deposit" and it has virtually no adhesion usually. 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. 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 or Bon-Ami [link is to product info at Amazon] as an alternate to caustic cleaning.

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

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

Ted Mooney, P.E.  finishing.com Brick, New Jersey

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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 gloves 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 beaker.
2. Add 100 cc of white vinegar, 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.

Tom Pullizzi Platronica.com Falls Township, PA

 

Hello, Where can I buy some ethylene glycol? Where can I get chemistry equipment in general? I have been searching the net but can only find industrial sites. I don't really need 1 MT of CuSO₄!

Great site by the way. Kudos!. Am I correct in assuming that the above formulae for copper plating doesn't require CuSO₄?

Thanks for your help.

Eamon Captian
- New York

Thanks for the kind words, Eamon. I believe that standard automotive anti-freeze is ethylene glycol. Yes, you are correct that Tom has described a plating process that does not require copper sulphate.

Ted Mooney, P.E. 
finishing.com
Brick, New Jersey

Suggestions: I tried your household plating experiment and needed to make the following revisions -

ABSTRACT

1. Pickle object to be plated in sulfuric (battery) acid, found at auto parts stores or large chain stores.

2. Solution Prep

a. Prepare solution as directed

b. Use a piece of copper sheet metal

c. Attach scrap metal to wire connected to negative clip of 12 volt battery charger

d. Attach copper to positive terminal

e. Turn on and shake off solid particles that form after a while

f. Let the part sit for about a hour and a half - until the solution is bluish when observed from the side

The solution is now ready to use as prescribed by your directions. This formula has been tested 25+ times. Thank you very much.

John Markgraf

My ol' dad was keen to try and copper plate some leaves but couldn't get the copper to 'stick'.

I sprayed the leaves first with zinc plate (ordinary aerosol can of zinc undercoat [link is to product info at Amazon] for car bodywork) then dunked these in an ice cream tub of copper sulfate [link is to product info at Amazon] with just a tiny drop of H₂SO₄ (from my car battery) and connected the car battery charger to a piece of copper pipe (about 8 inches) and the other side to the coated leaf. I did put a small 12 volt bulb in series with it all to limit the current but I ended up with quite a nice copper coated leaf. My old man was highly delighted.

John Rostron
- United Kingdom

I am looking for a reasonably simple process in which I can plate copper metal onto a nonconducting substrate such as Kapton or Mylar (both plastics). Electroless would be preferable, but not necessary. If anyone knows of a particular kit I could purchase that would be even better, although not necessary.

Nikolas Uhlir
- Alexandria, VA

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).

PHILIP CAMP
- PHENIX CITY, AL, USA

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