Brass electroplating for amateurs and students

A. Hi Blake. Are you sure your anodes were solid brass not brass plated steel (which will dissolve as rust)? If solid brass, I'm not sure why the solution is orangish-brown; perhaps if you used finer filter paper that color will be removed.

But I'd suggest that you try either copper plating or zinc plating, both of which are quite do-able by amateurs. Unfortunately you will find home-brew brass plating impractical. The reason is that brass is an alloy/mixture of zinc and copper and what will happen when you try to plate it out is that you will plate out only copper. No zinc will plate out at all as long as there is any copper in the solution. Read on for more info about why this is so.
Luck & Regards,


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

A. Hi Idris. The reason is already explained on this page, but it's both a bit buried and somewhat complicated, so I'll try to answer your question specifically.

Brass is an alloy of copper & zinc. To achieve brass plating you therefore need to electrodeposit both copper & zinc, and in relatively equal proportion (a plating with one part zinc to a thousand parts copper, for example, would not be brass colored). But this is not easy to do because the zinc is unwilling to electrodeposit.

The reason zinc doesn't electrodeposit is because copper is much, much, more noble than zinc (+0.337V vs. -0.763V, as you will see if you consult an 'electromotive force' or 'electromotive series' table). In fact, if you put a piece of zinc into a copper sulfate solution, it will immediately become coated with copper because ions of Cu⁺⁺ in the copper sulfate will steal electrons from the zinc metal atoms and deposit as Cu⁰ metal atoms while causing the zinc metal atoms (Zn⁰) to become Zn⁺⁺ ions dissolved into the solution. That is why you cannot electrodeposit brass from a solution of copper sulfate and zinc sulfate.

We get a little more complicated now by noting that those electromotive force numbers from the table are at standard concentrations. Those potentials shift a little bit at different concentrations, and the 'Nernst Equation' gives us the actual math behind that shift.

E = E^• + (0.059/n) logC

Fully understanding the derivation of the Nernst Equation, and working it is quite difficult, but what will be apparent is that "0.059 logC" means that a huge change in Concentration is necessary for even a small change in E.

What you would find if you worked that Nernst Equation is that if you could make the solution contain billions of times as many zinc ions as copper ions then their potentials would be roughly equal so you could deposit brass. However, there would obviously be so little copper in the solution that any copper would be deposited in a microsecond and you would just be depositing zinc thereafter -- so that's a theoretical answer but not a remotely practical one.

On to cyanide ... what it does is it 'complexes' or ties up the copper so there are virtually no free copper ions. It gives you that desirable situation where free zinc ions in the plating solution can outnumber free copper ions by billions to 1, achieving (per the Nernst Equation) approximately equal electromotive force for the zinc and copper. Unfortunately cyanide is not only a fatal poison as a liquid but it can fairly easily become airborne as hydrogen cyanide gas, and be inhaled with fatal result.

Luck & Regards,


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

A. Cyanide-free brass plating:
8 gms copper carbonate / 8 gms zinc oxide/ 260 gms potassium sodium tartrate / 40 gms sodium hydroxide / 1 lit water, brass anode,0.5-0,7 A/dm2, 50 °C temp., pH 13,2-13,6

variant 2:
copper sulphate 40-55 gms / zinc sulphate 35-55 gms / potassium sodium tartrate 380-420 gms / sodium hydroxide 80-100 gms / 1 lit water, 1-1,5 A/dm2/temp.45-50°C, brass anode

Hope it helps and good luck!

A. Dear Linda:

Commercial brass plating processes are based on cyanide and as such should not be performed in a hobby or school environment both from a personal safety point of view and potential environmental impact.

There are reports of a commercial non-cyanide process being available, however I have no information regarding source.

To achieve a "brass like" appearance it would be more advisable to contact one of the lacquer suppliers listed in the supplier section of finishing.com. I believe some of them have products which can produce a simulated brass appearance.

A. Hi Linda. If possible, see if you can talk the student into a different type of plating like maybe nickel, or zinc, or copper. Brass is a special problem because it's an alloy of two metals, copper and zinc. You may have done 'lemon batteries' in class where you put pennies (copper) and galvanized nails (zinc) into a lemon and see that it generates more than a full volt of electricity; the copper wants to plate out and the zinc wants to become/remain dissolved and it won't plate out, more copper plates out instead.

The way professionals get the zinc to deposit is to"complex" or "tie up" the copper with poisonous cyanide. Although proprietary non-cyanide complexers may exist, I'm not sure if the vendors will offer it to students and amateurs, and they're probably very tricky to successfully operate.

As Ken says, if the aim is decorative, your student can apply a brass-toned lacquer which is actually commercially done these days on furniture and lamps as a replacement for brass plating; if the aim is education and practice in electroplating, there's plenty to be learned from plating one of those other metals I mentioned which don't require cyanide.

One other possibility might be to plate copper onto the item first, then plate it with zinc, and then to heat it over a bunsen burner to see if you can get the zinc and copper to diffuse together into brass. I have heard of students making brass colored pennies by zinc plating them and then diffusing the copper and zinc with a bunsen burner or torch.

Luck & Regards,

A. Hello Craig.

The best plan of course would be to get preplated parts. If the parts do not need to be highly decorative, and are not special high-strength steel, zinc plated nuts and bolts are available at the hardware store. If they need to be decorative, I have seen nickel-chrome plated nuts at motorcycle stores, and brass ones may be available as well.

If you want special parts plated, jobshops offer that service, and they are equipped and operated by trained employees--so that would be the second choice.

Yes, it is possible to electroplate yourself, but it can be complicated, and it has safety and environmental implications -- especially in the case of brass plating (the solution is almost always cyanide based), or chrome plating (which involves carcinogenic and tightly regulated hexavalent chromium). Further if those bolts are high strength, electroplating will cause hydrogen embrittlement, which means they can fail like brittle glass unless you immediately also employ the proper baking procedures to relieve the embrittlement.

The plating process usually includes:

Stripping off the old nickel plating with cyanide-based strippers or Metalx (Ronatec.us) [a finishing.com supporting advertiser] proprietary nickel strippers (although sometimes it can be sandblasted off). Then, mechanical polishing and buffing (if the surface is not smooth and free of fine scratches, electroplating will not make it so!). It takes a lot of experience to get good at buffing, but is certainly something you can learn. Next the parts are electrolytically cleaned to a water-break free degree with proprietary mixtures of strong lye and detergent. Then the surface oxides are removed with hydrochloric acid. Now the parts are electroplated: sometimes with copper and buffed again, but always with nickel--sometimes two or three different proprietary layers. Then you apply the final plating, be it brass, chrome, or gold.

I would suggest either buying the parts plated, finding a plating job shop to do them, or perhaps painting them. If you want to learn electroplating for yourself, it is doable, I certainly don't want to discourage you -- it's just not easy, there are safety issues (especially for cyanide-based platings like brass) and there might be environmental issues. If you're determined to practice, please try nickel plating first.
Good luck!

A. Hi Matthew. Please remember that the Baghdad Battery is a blue-sky theory, is is not a device! According to the Discovery Channel, a stopper made of cork and a few shards of a pot were found (as in all digs); but in reasonable proximity some copper and iron fragments were also found that truly don't look like much :-)

But in wild speculation for TV, scientists used those tiny shards of pottery and blobs of metal to arrive at a battery theory ... then they made computer images of what they guessed it could have looked like IF it existed.

Many archeologists feel that these fragments were just miscellaneous ceremonial knick-knacks that happened to found near each other, and that it's a disservice to history to present crazy computer graphics in such a fashion as to imply that anything even remotely resembling those computerized conjecture images was actually ever found, that it's total nonsense!

This is NOT to say there absolutely was not a Baghdad Battery! It's only to say that the evidence for a battery seems very very thin to date, and the pictures you've seen are only computer-generated wild speculation -- using those computer graphics speculations to jump to the conclusion that the ancients must have known electroplating is not well founded.

My personal belief is that it didn't exist -- because hydrogen gas is always generated when electroplating is attempted, and mankind has always desperately wanted to fly. If the Baghdad Battery actually existed, hydrogen would surely have been collected and investigated, and we'd have had people riding in hydrogen balloons thousands of years ago.

You can surely do plating yourself; we have an FAQ showing elementary school children how to do it. The question is whether you can do truly useful plating yourself. And the answer to that is that silver probably can't be safely and robustly electroplated by an individual without significant experience. However, there are simple "wipe-on" silvering solutions that may suffice. Please see our FAQ: "Silver Plating at Home". Good luck!

A. A fascinating page at Smith College, thank you for that link. But "A recipe no more makes a cook than sermons make a saint". And you only have a recipe for making a battery, we need a lot more information to see if the ancients really plated gold onto silver with any success. I don't doubt it, I just don't know how they did it.

Brush plating kits are a proven technology. How you apply it depends upon your skill and training. Most people (including me) would say that brush plating of a car emblem or touching up a small (1 square centimeter) of a car molding is a more realistic task than brush plating a trumpet.

Good Luck!
Regards,

A. I would add that gold plating a car emblem usually involves just stripping off a very thin layer of chromium, and electroplating gold onto the beautiful OEM-prepared high quality multi-layer nickel plated emblem. The trumpet is not only much bigger, but is a mix of oxidized brass and worn silver; further, silver electroplating requires cyanide based solutions whereas gold doesn't. It's a much bigger job. Please try the "wipe-on" silvering first, and only move on if it doesn't work to your satisfaction. Good luck.

Regards,

A. Years have passed since the last post but I found this page in searching for a way to electroplate brass on my own. New developments in the sciences have come to the rescue for those who are hobbyists and wish to do their own electroplating, anodizing and metal finishing. I have no affiliation with companies producing the kits for these purposes, however, I have tried some of their products and they work. The skill required is no more than that required of a decent handy person. If you have skill in welding, fixing wiring or any number of routine skilled jobs, you can do your own electroplating. If you have two left thumbs and can't start a balky lawnmower, don't waste your time.

Complete kits are available for the hobbyist that do not involve cyanide or other deadly chemicals. Are they as good as the results of a professional plating shop? Maybe, maybe not. You judge. I'm happy with my results.

Thanks Ken. Many of the world's bench jewelers fancy themselves platers but scoff at platers who think of themselves as jewelers -- and so it goes :-)

If the substrate is an easy one, as jewelry is, and there is no mass production, then plating can be quite easy. And gold plating of car emblems is something anyone can do -- because the OEM did 99% of the work, and all the hobbyist needs to do is strip off a few millionths of chrome, and put gold in its place on top of a perfectly prepared, corrosion resistant, shiny, bright nickel plated item.

Still, the EPA chose electroplating to be the very first "categorically regulated" industry in America. With slight simplification, this means if any liquid was used in an electroplating business, it is regulated waste. "New developments in science" make no difference because it's based on the 'electroplating category'. Every bucket of water, every drop of hose water that splashes on the floor is regulated. It's not a matter of whether I want you to electroplate, it's a matter of whether the US government does, so look up EPA 40 CFR 433 (it's on the net).

If you do electroplating well, you may start charging people for the parts or the service. And once you do, you've become part of an industry that is subject to complex permitting rules. Odds are strong that small plating shops won't be caught, and if caught won't be prosecuted, but I personally know a man who served penitentiary time after plating in his attached garage, getting sucked in by degrees, and getting caught illegally disposing of wastes when he found that legal disposal was so expensive it would have meant telling his wife and family that they were losing their house.

If hobbyists want to electroplate, they should realize its hazards, environmental impact, and their own usual lack of training; but most importantly they must realize that if it goes from hobby to small business they're subject to regulations that have ensnared others. Good luck.

A. Hi, Frank. Plating is drop-dead easy, but useful, robust plating is harder, and it depends on what you want to do. Brass plating without deadly cyanide, or chrome plating without toxic hexavalent chrome is one of those things that is 'complicated and skill-intensive' ... but zinc plating, copper plating, nickel plating, gold plating, rhodium plating, etc., are all safer and have less environmental impact.

What I would probably do is polish the existing backplate with rubbing compound [on eBay or Amazon], metal polish, or a more powerful buffing compound and a buffing pad on some sort of power tool (Dremel or cordless drill). My bet is that it is either solid brass, which will polish and can be lacquered, or that there is bright nickel plating underneath that brass which, with care, can be polished down to the bright nickel plating. Then I would apply a brass-toned lacquer. It will cost very little, you'll learn something hands-on, and if it doesn't satisfy you can send it to a plating shop.

Regards,

A. For small parts you could try using an old blacksmith technique - mechanical peening with supplied heat energy to help the process along.

See this video …

A. Hi Pete.

1. Decorative chrome plating is actually a very heavy layer of bright nickel plating followed by a very thin layer of chrome plating (see our Introduction to Chrome Plating), so it's relatively easy to strip the chrome but leave the nickel, and then brass plate it. But what might be better is to just apply a brass-tone lacquer.

2. Brass plating over steel will be quite matte. The usual technique is to plate the steel with bright nickel first.

3. Stripping the clearcoat will depend on what it is. Brass lacquer is easily removed with lacquer thinner [on eBay or Amazon], but tougher clear coats may require toxic methylene chloride or boiling hot caustic.

4. Answer 4 is the same as answer 1.

Luck & Regards,