Question

Which of the following metal doesn’t possess a trans passive region?

(a) Iron

(b) Titanium

(c) Nickel

(d) Aluminum

This question was addressed to me during an online exam.

My question is based upon Modern Theory Principles topic in portion Modern Theory Principles of Corrosion Engineering

Answer 1

The correct answer is:

(a) Iron

Explanation:

The transpassive region is a specific region in the electrochemical behavior of certain metals, where the metal undergoes an increase in corrosion rate after reaching a certain potential. This is typically observed in metals like titanium, nickel, and aluminum, which form protective oxide layers and exhibit a transpassive region at higher potentials, beyond which the oxide layer breaks down.

Iron, on the other hand, does not exhibit a transpassive region in the same manner. Instead, it tends to corrode steadily in acidic environments without the formation of a protective transpassive oxide layer like those seen in titanium, nickel, and aluminum.