Question

In which of the following reactions, we observe an increase in corrosion rate with the increase in corrosive concentration?

(a) 18Cr–8Ni in HNO3

(b) Ni in NaOH

(c) Pb in H2SO4

(d) Fe in H2SO4

The question was asked in an interview.

This question is from Effect of Temperature and Corrosive Concentration topic in portion Corrosion Principles of Corrosion Engineering

Answer 1

Right choice is (d) Fe in H2SO4

The best I can explain: Iron in sulfuric acid, the corrosion rate of iron increases at first and then it decreases with an increase in corrosive concentration. This is because, at low concentrations, iron will dissolve in sulfuric acid whereas at high concentrations it forms a passive layer on the sample surface.