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topic 9622

Use of cyanide in decorative chrome plating


What is the value of a potassium cyanide bath in decorative chrome plating? My company makes motorcycle mufflers and we were told that a cyanide bath would significantly improve the chrome's ability to "level". Is this essentially correct?

James O'Grady
- Salinas, California, USA

First of two simultaneous responses -- (2001)

A. Never put any type of cyanide in an acid chrome plating solution. It will release poisonous hydrogen cyanide gas. The same thing used in death row gas chambers. Whoever was telling you this is greatly misinformed or the communication has gotten mixed up somewhere.

Rick Richardson, MSF
Dayton, Ohio

Second of two simultaneous responses -- (2001)

A. I think James, or the person who was instructing him, was not referring to putting cyanide into the chrome plating bath but was talking about an undercoat of cyanide copper plating under the nickel plating.

The great majority of bumper plating shops have stopped doing copper plating, electing to put the steel parts directly into a nickel plating bath. There are, however, old timers who feel that an underlayer of buffed copper gives a deeper shine and better reflectivity. I call them "old timers" rather than "old fashioned" advisedly. I don't scientifically know for sure that a buffed copper underplate really makes for a deeper shine or not, but I do believe it. I feel that most chrome plated bumpers today do not have the reflectivity of the best of yesterday's; and I feel that Harley chain guards, which have the buffed copper layer, are shinier than any bumpers. But I don't know if this is actually related to copper plating per se or to today's shortcuts in the mechanical polishing process.

The optics people have ways of quantifying the resolution available from a lens or a mirror, so I don't know why we in the finishing industry should be unable to specify the "resolution" of a reflective plating.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

April 11, 2012

A. The copper used by the old timers is likely for Concours d'Elegance automotive restorations, where the plating should match or exceed the original quality.

Rusty Springfield
- Springfield, Illinois, USA

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