Plating Q&A: Converting a Brass Plating Bath
How do you convert a brass plating bath into a bronze plating bath?
Q. Can a brass plating bath be converted into a bronze plating bath?
A. Conceptually, converting a brass plating bath into a bronze plating bath is possible, though the conversion depends on the type of brass plating bath you are using.
|
Brass Plating Bath |
|
|
COMPONENT |
CONCENTRATION |
|
Copper cyanide |
4 oz/gal |
|
Zinc cyanide |
1.25 oz/gal |
|
Sodium cyanide |
7.5 oz/gal |
|
Sodium carbonate |
4 oz/gal |
|
OPERATING CONDITIONS |
RANGE |
|
Metallic copper |
2.8 oz/gal |
|
Metallic zinc |
0.7 oz/gal |
|
Free cyanide |
2 – 2.5 oz/gal |
|
Temperature |
75 – 100°F |
|
Current density |
3 – 5 ASF |
|
Voltage |
2 – 3 volts |
|
Anodes |
Brass 80% copper / 20% zinc |
|
Bronze Plating Bath |
|
|
Component |
Concentration |
|
Copper cyanide |
4.0 oz/gal |
|
Zinc cyanide |
0.3 oz/gal |
|
Sodium cyanide |
5.0 oz/gal |
|
Rochelle salt |
2.0 oz/gal |
|
OPERATING CONDITIONS |
RANGE |
|
Metallic copper |
2.8 oz/gal |
|
Metallic zinc |
0.17 oz/gal |
|
Free cyanide |
0.3 oz/gal |
|
Temperature |
75 – 100°F |
|
Current density |
2 – 4 ASF |
|
Anodes |
Brass 92% copper / 8% zinc |
The two plating baths are quite similar. By slightly altering the composition of the bath, you can change the color of the deposit, resulting in a brass or bronze finish.
But then is the bronze bath a true bronze? This is where you have to take into account the parts that you are plating and their use. A true bronze has different physical properties compared with that of the bronze that consists of only copper and zinc. Typically, a bronze consists of copper and tin. While the copper zinc bath will give you a bronze-like color, is not a true bronze.
My advice is to not convert your brass bath, particularly if it is functioning well. It would be better to prepare a separate bath that is a true bronze plating bath using copper and tin.
Originally published in the September 2015 issue.
Related Content
-
3 Tests to Ensure Parts are Clean Prior to Plating
Making sure that all of the pre-processing fluids are removed prior to plating is not as simple as it seems. Rich Held of Haviland Products outlines three tests that can help verify that your parts are clean.
-
Successful South African Plater Beating the Odds
Remaining focused on quality and reliability, Team Plating Works stays profitable in a volatile and challenging economy.
-
Products Finishing Reveals 2024 Qualifying Top Shops
PF reveals the qualifying shops in its annual Top Shops Benchmarking Survey — a program designed to offer shops insights into their overall performance in the industry.
