What is bronze, and how does one bronze plate? N. P.
Good question! Bronze is an alloy consisting of copper and tin. Sometimes other metals are added to improve toughness. Bronze can be plated as a decorative finish and is sometimes used as a substitute for nickel. The color of the deposit can vary from copper color (2–3% tin) to white (> 20% tin). Many different plating baths have been used for plating bronze, with cyanide and pyrophosphate being the most common.
A typical cyanide plating bath is as follows:
|Sodium stannate||100 g/liter|
|Sodium cyanide||28 g/liter|
|Copper cyanide||12 g/liter|
|Sodium hydroxide||10 g/liter|
|Sodium cyanide, free||16 g/liter|
|Sodium hydroxide, free||15 g/liter|
|Temperature||140 – 160F|
|Current Density||20 – 50 ASF|
A very recent paper discusses decorative bronze plating in detail: N. V. Mandich, Metal Finishing Magazine, June 2003.