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How to calculate plating amps and time

August 27, 2008

How is the etch ; amps and duration time (sec.)
" " strike; amps and duration time (sec.)
" " plate; amps and duration time (sec.)

calculated for a given part?

Brian S.
shop employee - Buffalo, New York

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Hi, Brian. There is a chemical principle behind your question and it's called Faraday's Law of Electrolysis. It will tell you how many amp-minutes are required to move how much metal. If you look in the appendices of the Metal Finishing Guidebook there is a chart which takes into account Faraday's Law and the density, atomic weight, and oxidation state of the various plateable metals, and gives you the thickness that will be deposited in so much time and so much current density.

But there's a big "however". While it's fairly easy to determine the product of amperes and time that will be required for a given amount of plating, very complex phenomena determine the current you must apply to get satisfactory plating, and you're not going to be able to calculate that. For example, if you determine that you need 800 ampere-minutes for the desired thickness, that doesn't imply that you are free to choose 400 amps for 2 minutes, or 2 amps for 400 minutes. You may find that you must plate at 40 amps for 20 minutes, with little latitude for variation without burning or losing brightness.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 28, 2008