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topic 28032

Electroplating with Brass (Electrodeposition of Brass)



A discussion started in 2002 but continuing through 2019

2002

Q. Sir,

We currently do Copper plating & then brass plating on M.S. Hinges. I would like to know
1) is there any problem in doing brass plating over cyanide copper plating on M.S. articles
2) Is there any risk in doing only brass plating on M.S articles, even if the lacquer is of good quality?

Rajesh Bhargava
Raj Industries - Delhi, India


2002

A. Either approach should be okay, but if you are looking for bright brass an easier way to go may be with nickel plating under the brass.

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



2004

Q. Brass is an alloy of zinc and copper. How then is it possible to electroplate with brass? Why doesn't the brass dissociate in the bath into copper and zinc?

Gordon James Stopps
hobbyist - Toronto, Ontario, Canada


2004

A. Hi Gordon. It does dissociate into copper and zinc ions. And then the copper and zinc ions deposit on the item to be plated and are reduced to copper and zinc metal, creating the brass alloy.

That is not to say it's easy to brass plate--there are difficulties: for example, copper is a much more noble metal than zinc, so we would expect the deposit to be virtually pure copper if it were plated from a simple salt (students make 1.1 volt lemon batteries and potato batteries by putting a galvanized nail and a copper penny into a lemon; that's how powerfully the copper wants to come out of solution compared to the zinc).

But when copper cyanide and zinc cyanide are mixed in a reasonable ratio, the cyanide fights hard to hold onto the copper, so the concentration of free copper ions is very low, so you are able to plate the brass alloy. Cyanide is a dangerous chemical and there are other complexers these days that allow brass plating -- but you can't do it out of a simple chloride or sulphate salt.

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



Need to Speed Up Deposition in Brass Plating

2003

Q. What are the conditions of work of a brass bath to get a good speed of deposition in brass bath top layer?

Diogo Cavalcanti
Home Hardware - Caxias do Sul, RS, Brasil


2003

A. Hi Diogo.

The only thing that can be done and must be done to increase the plating speed is to increase the current density -- because moving electrons from the anode to the cathode via electric current is, according to Faraday's Law, what makes a proportional number of metal ions move from the anode to the cathode.

affil. link
"Electrodeposition of Alloys: Principles & Practice"
by Abner Brenner
from
from Abe Books
or
info on Amazon
or
see our Review

How to achieve this, while avoiding consequent problems like burning, is, of course, difficult to resolve in the abstract. But impelling jets of solution onto the cathode at high speed is perhaps the most promising way, since it minimizes the thickness of the boundary layer through which the ions must diffuse and, by rapid replacement of solution, it also keeps plenty of metal ions available, rather than having the area starved for metal.

Are you using a cyanide or non-cyanide brass plating bath, Diogo?

It may be possible to increase the temperature of the bath, which leads to greater ion mobility and thus theoretically allows faster plating speed, or to increase the metal concentration -- but these things may also affect the "balance" of the bath (Copper is far more noble than zinc, so it's quite a trick that we are able to plate brass at all :-)

You might be interested in Brenner's "Electrodeposition of Alloys", because as you change voltages, currents, temperature, and concentration you have a propensity to change the alloy composition. Best of luck, and get back to us.

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



April 15, 2014

Q. Good evening,
I need the answer for the following questions in detail:

Q1: when we use low voltage in the electroplating of brass, we noticed that the zinc ions are deposited rather than the copper and the color was white? We use brass plate as anode and spoon as cathode and brass solution contains:
   - 40 grams of brass salts (copper sodium cyanide and zinc sodium cyanide),
   - sodium sulphite, and sodium cyanide,
   - and we add ammonium chloride to the solution
We fix the temperature, distance between cathode and anode, pH (9.8-10.8) copper content 60% and zinc 30% in solution and just change the voltage.

Q2: Write the oxidation-reduction reaction which occurs in the brass solution?

Q3: Why do we use ammonium chloride and sodium sulphite and sodium cyanide in this solution?

Q4: What are the advantage of using the cyanide bath in brass electroplating?

Brass solution : Zonax brass 75 g/l and 3 g ammonium chloride. Brass contains 70% copper And 30% zinc

ammar othman
electroplating student - jordan-amman


A. Hi Ammar. Sorry that no one helped you yet. Perhaps if you started with one particular question where you need help, the results might get better since no stranger is going to complete your entire lab project for you (and questions 2 through 4 look like they might be copied right off your assignment :-)

But as for Q1: As mentioned earlier, copper is far more noble than zinc, and will preferentially deposit from a simple salt. To counteract that and make brass plating possible, it is necessary to complex the copper with cyanide, to greatly reduce the number of free copper ions available for electrodeposition. Even when this is done, however, it requires careful balancing of all parameters to get a balanced deposit of copper and zinc. Your experiment demonstrates that if the voltage is very low, things go out of balance, with the copper too complexed for any of it to deposit; but if you increase the voltage, you overcome the complexing sufficiently to deposit a proportion of zinc.

affil. link
"Modern Electroplating
Lowenheim"

from Abe Books

or

It is noted in Lowenheim's "Modern Electroplating" =>
that with some brass plating baths the proportion of zinc rises with higher current density, and for others it decreases. He includes a graph by Compton, Ehrhardt, & Bittrich for one bath which exhibits highest zinc concentration at about 0.3 A/dm2, and declining whether the current is increased or decreased. Lowenheim has an excellent theoretical and practical treatment of brass and other alloy plating baths. Please try to find a copy in your school library; if it's not there, and you can't find another good book on the subject, please suggest it to your advisor. Good luck.

Regards,

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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
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April 4, 2016

Q. Sir,

Please explain to me about Brass electrolyte.

Rate of deposition of zinc and copper?

What is the ratio of metal deposits from electrolytic solution and anode?

santosh tiwari
- Delhi, India


April 2016

A. Hi Santosh. Most brass plating electrolyte are cyanide-based, and the cyanide complex allows practical ratios of copper and zinc to be deposited for brass deposits (today there are also some proprietary brass plating baths available that do not require the use of cyanide).

"Modern Electroplating" describes the composition of 10 different cyanide-based plating baths and includes 233 references. It is the best starting point that I know of for a theoretical investigation; but what people visiting this page may not necessarily realize is that, in general, users do not attempt to formulate electroplating baths; rather they purchase them from suppliers who have spent years perfecting them, and offer them as proprietary processes. Good luck.

Regards,

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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


April 19, 2016

A. The Cu/Zn ratio in the deposit is not, as you might think, determined by the Cu/Zn ratio in the bath. It depends more on the cyanide/zinc ratio.

pH control is also crucial. There are two different levels at which brass is plated - one in the mid tens, one in the upper 11's, if memory serves.

Do some library research. This information is out there.

dave wichern
Dave Wichern
Consultant - The Bronx, New York



February 28, 2019

Q. Want to do natural brass finish plating (reddish brass finish) on nickel plated or copper plated surface; we are using cyanide based bath.

vasanth kumar
Gold & brass plating - chennai,Tamil nadu, india


February 2019

A. Hi Vasanth. Red and other color patinas can be applied to brass, but I think I am understanding you to be saying you just want your deposited brass plating to be more on the reddish side, i.e., higher in copper. The previously mentioned "Modern Electroplating" [affil. link to book on Amazon] has all kinds of graphs on the subject, and notes & exceptions & provisos, but the general trends are higher current density, higher temperature, and lower pH generally move towards higher copper content. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



April 25, 2019

Q. My company has met some problems of electroplating with brass (imitation gold color). We are using cyanide-based bath and Our problem is that when we finish the brass plating after water cleaning, blowing dry and baking, there would appear not obvious red strips on the sample surface. At first, we think that was caused by the water stain but after we strengthen the blowing dry the red parts were still at. Can anyone give some suggestions to improve our problems.

Jimmy, Chung
ziyong enterprise co., ltd - Tainan, Taiwan



October 12, 2020

Q. Hello sir, I am doing a lot of work for developing cyanide based brass salts as follows: 70% copper cyanide, 35% zinc cyanide, ammonium chloride, sodium cyanide as free cyanide, sodium bicarbonate, sodium sulphite and potassium sodium tartrate and a bit of sodium thiosulphate ... but I did not find the satisfactory result. Please suggest what should I do to obtain yellow colour of brass ... please help.

Mohd malik
- Tamil nadu, India


October 2020

A. Hi Mohd. There are many possible formulations for brass plating. Yours may be a perfect one, but unless a reader has worked with that particular formula they may not be able to suggest what needs adjustment. So please tell us where you found it because with a reference people can have more confidence that it's workable.

Here's what Lowenheim suggests in "Electroplating" [affil. link to book on Amazon]:

28032-1brassFormula

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


October 13, 2020

Q. Thank you so much for your valuable reply.
Sir I am working with electroplating industry.
Since last seven years and already developed rochelle copper salt, chrome salts, nickel sulphate and chloride and copper sulphate. Sir I had developed these products by doing a lot of study by many means like some patents, etc.
Please please suggest me what should I have to do for brass salt if I want to make it only 10 kgs. What will be the compositions for this salt ... what should i have to add in it or remove from it. Please help me sir.

Mohd malik
- Tamil nadu, India


October 2020

A. Hi again, Mohd. I think you misunderstood me :-(
I am not a chemist and have not spent years developing formulations like you have. My point was that we can offer you published formulations for brass plating solutions, but I certainly can't, and I doubt that anyone can, look at your formulation and tell you what needs tweaking :-)

Here are a number of formulations from Lowenheim's "Modern Electroplating" [affil. link to book on Amazon]:

28032-2brassFormulas

sidebar

Note to readers: We generally don't photocopy whole charts & tables from books, potentially depriving authors of some of the reward for their efforts. But we made an exception with these two Lowenheim books because: he passed away 40 years ago; he was a luminary whose work is not widely enough recognized; his daughter Trudy Hayden found us, gave us for free and encouraged us to distribute, a number of copies of his books -- so we know his family is not losing any money via this photocopying, and is happy that his work continues to be appreciated.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


October 15, 2020

thumbs up sign I was thinking I would like to use some 1" OD copper pipe for a handrail, but then thought bright brass would be nicer. So, could I plate a piece of pipe? Your answers were excellent, to the point. So, I abandoned the idea as soon as I saw 'cyanide' But, what a great and informative web site. Thank you!

Tony Bridgens, P Eng., retd
- Orillia, Ontario



Brass plating iron - What solution is required?

October 26, 2020 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi there,
Greetings,

I want to plate iron using brass (Yellow copper). I have good information about electroplating but my question is how to make the standard bath solution with minimum chemicals because nothing is available in my country.

Thank you and appreciate your help.

Regards,

Awder Hussein
- Sulaymaniyah KRI Iraq


October 2020

A. Hi Awder. We appended your question to a thread which includes the brass plating formulas from Lowenheim's books. But you should probably check the libraries for a copy of one of his books because there's more to surgery than choosing the scalpel :-)

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


November 6, 2020

Hi,
I'm working on setting up non-cyanide bath for brass electroplating in my shop. Can you please give me what chemicals I need to prepare the solution?

I found below from a source:

Copper sulfate 5-10 g/L
Zinc oxide 0.3-1 g/L
Sodium hydroxide 60-100 g/L
Glycolic acid 5-20 ml/L

Operating Conditions
Range
Current density 10-12 ASF
Additives Gelatin at a concentration of 0.5 g/L recommended for a smoother deposit.

Can I go with that?
I read many books for the past 2 months but still I need your consultation.

Thank you so much.

Ahmed Abdullah
- Iraq Baghdad Center


November 2020

A. Hi Ahmed. What is the source of that formula? We don't like to post formulas except with their published sources because we are concerned about violation of copyrights and crowd-sourcing of trade secrets.

I hope someone can help you, but Lowenheim says in Modern Electroplating (1974):

" ... Lainer, after studying all the various types of brass plating baths investigate before 1960, concluded that so far there are no satisfactory alternatives to cyanide brass electrolytes ... It is still believed that Lainer's 1960 conclusion is correct."

There may or may not be satisfactory proprietary alternatives here in 2020 but I would be surprised if you can home-brew a robust cyanide-free brass plating solution.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


November 6, 2020

Q. Thank you Mr. Mooney for your reply,

Actually the source of the above formula returns to one of my chemistry friends and the copyright is well noted.

But I considered more than 5 books and sources that there is a way to accomplish non-cyanide bath plating at least in a small scale.

I hope someone could help me on this regard.

Appreciated

Ahmed Abdullah [returning]
- Baghdad Center, Iraq

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