Problem 4 A cylindrical steel tank is coated with a thick la

Problem 4

A cylindrical steel tank is coated with a thick layer of zinc on the inside. The tank is 50 cm in diameter, 70 cm high, and filled to the 45 cm level with aerated water. If the corrosion current is 5.8 10^-5 A/cm^2, how much zinc in grams per minute is being corroded?

Solution

>> Let Zinc Loss is \'w\'

>> As, according to Farady\'s Law

w = ItM/nF, where

I = Current = Current Density*Area = J*A

Current Density, J = 5.8*10^-5 A/cm²

A =Area = Exposed Area of Zin wih aerated Water = pi*d*h,

d =dia of tank = 50 cm = 0.5 m

h = height upto which Zn is in contact with aerated water = 45 cm = 0.45 m

=> A = pi*0.5*0.45 = 0.7068 m² = 7068.58 cm²

=> I = J*A =  5.8*10^-5 * 7068.58 = 0.401 A

>> M = Atomic Mass of Zinc = 65.38 g/mol

n = Valency = 2

F = Faraday No. = 96500 C

t = time in seconds = 3600 s/h

>> Putting all in the above equation,

w = (0.401 A)*(3600 s/h)*(65.38 g/mol)/(2*96500 C)

Solving,

w = 0.489 g/hr .......ANSWER....REQUIRED ZINC LOSS.......