Calculating Electroplating: A Guide

Electroplating is a process where the ions of a metal are transferred by an electric field in a solution to coat a conductive object. Cheaper metals like copper can be electroplated with silver, nickel or gold to give them a protective coating. A common application of this was with the production of automobiles, where steel parts were plated with copper, then nickel and finally chromium to give outdoors temperature and weather protection. We can calculate the time it will take to electroplate 1 mole of the metal given the metal being electroplated and the current being applied.

Step 1

Look at the chemical equation to determine how many electrons are needed for 1 mole of the metal being electroplated. Using an example, if we take copper Cu as our metal with 25 amps, then each mole of copper Cu++ will require 2e- electrons.

Step 2

Use the equation:

(Q=n(e)F)

to solve for Q. Q is the amount of electricity or charge in coulombs C, n(e) is the number of moles of electrons and F is the Faraday constant 96,500 C mole-1. Using our example where we need 2e- for each mole of copper:

(Q=n(e)F=2text{ mol}times 96,500text{ C/mol}=193,000text{ C})

Step 3

Determine the time it will take to electroplate out one mole of the metal using the equation t = Q/I. Q is the amount of electricity in coulombs C, I is the current in amps A and t is the time in seconds. Using our example:

(t=frac{Q}{I}=frac{193,000text{ C}}{25text{ A}}=7,720text{ s}=2.144text{ hours})

TL;DR (Too Long; Didn’t Read)

The equations can be reversed to calculate the amount of metal deposited when given the time and the current.