Question

Calculate the corrosion penetration rate of iron that corroding at an electrochemical corrosion rate of 1 microampere/sq. centimeters?

(a) 0.212 mpy

(b) 0.11 mpy

(c) 0.46 mpy

(d) 0.64 mpy

I have been asked this question during an interview.

My query is from Testing in section Corrosion Testing of Corrosion Engineering

Answer 1

The correct answer is (c) 0.46 mpy

To explain I would say: Corrosion penetration rate = K (ai/nD)

a = atomic weight of iron = 55.8 g

i = current density = 1 micrometer/sq. Centimeters

n = valency change = 2

D = density of iron = 7.86 g/cm^3

K = 0.129 for steel

Corrosion penetration rate = 0.129 * [(55.8) / (2*7.86)] = 0.46 mpy.