Question

Zinc is to be electroplated onto both sides of an iron sheet that is 20 cm2 as a galvanized sacrificial anode. It is desired to electroplate the zinc to a thickness of 0.025 mm. It is found that a current of 20 A produces a zinc coating of sufficient quality for galvanized iron. Determine the time required to produce the desired coating, assuming 100 % efficiency.

Answer 1

The time required for the coating is 105 s

Step-by-step explanation:

Zinc undergoes reduction reaction and absorbs two (2) electron ions.

The expression for the mass change at electrode
`(m_(ch))` is given as :

`(m_(ch))/(M) ZF = It`

where;

M = molar mass

Z = ions charge at electrodes

F = Faraday's constant

I = current

A = area

t = time

also;
`(m_(ch))` =
`(Ad) \rho` ; replacing that into above equation; we have:

`((Ad) \rho)/(M) ZF = It` ---- equation (1)

where;

A = area

d = thickness

`\rho` = density

From the above equation (1); The time required for coating can be calculated as;

`[ (20 cm^2 *0.0025 cm*7.13g/cm^3)/(65.38g/mol)*2 (moles\ of \ electrons)/(mole \ of \ Zn) * 9.65*10^4 (C)/(mole \ of \ electrons ) ] = (20 A) t`

`t = (2100)/(20)`

= 105 s