Question

A batch of 75 parts is to be nickel-plated in a barrel plating operation. The parts are identical, each with a surface area A = 5.3 in 2 . The plating process applies a current = 120 amps, and the batch takes 20 min to complete. Determine the average plating thickness on the parts

Answer 1

To solve this problem it is necessary to take into account the concepts related to electrochemical Machining Processes and metal removal. Metal removal rate is determined by Faraday's First law, which states that the amount of chemical change Produced by an electric current is proportional to the quantity of electricity passed, i.e,

$V = CIt$

Where,

V = Volume of material removed

C = Constant called the specific removal rate that depends on atomic weight (I attached a table with this values)

I = Current

t = time

Since we also have to consider the efficiency of the system to remove the Volume, of all the volume removed, only 95% will be efficient.

From our values we have to

$A = 5.3in^2$

$I = 120A$

$t = 20 min$

$C = 1.25*10^{-4} in^3/A-min$

$\eta = 95%$

Calculating the value we have that,

$V = (1.25*10^{-4})(120)(20)$

$V = 0.3in^3$

$V_{net} = 95\% *0.3$

$V_{net} = 0.285in^3$

The area is simply the calculation of the total units by that of each piece, that is

$A = 75*5.3$

$A = 397.5in^2$

Therefore we can calculate now the plating thickness through the ratio between Volume and Area

$d = \frac{V}{A}$

$d = \frac{0.285}{397.5}$

$d = 0.000716in$

Therefore the average plating thickness on the parts is 0.000716in