Question

Which of the following order is correct regarding the oxides of iron starting from metallic iron to gaseous oxygen interface?

(a) FeO, Fe2O3, and Fe3O4

(b) Fe2O3, Fe3O4 and FeO

(c) Fe3O4, Fe2O3, and FeO

(d) FeO, Fe3O4, and Fe2O3

The question was asked in quiz.

My question is based upon High-Temperature Corrosion topic in portion High Temperature Corrosion of Corrosion Engineering

Answer 1

Correct choice is (d) FeO, Fe3O4, and Fe2O3

For explanation I would say: The most oxygen-rich compound is found at the scale-gas interface whereas a metal-rich compound is found at the metal-scale interface. Therefore, the correct order is FeO(22.270% O2), Fe3O4(27.641% O2), and Fe3O4(30.057% O2).