The three iron oxides of steel scale are hematite (Fe 2 O 3 ), magnetite (Fe 3 O

Question

The three iron oxides of steel scale are hematite (Fe2O3), magnetite (Fe3O4), and wustite (FeO). Above 1,050 oF the most stable oxide is FeO.

    (a) Cooling below 1,050 oF causes the decomposition of wustite to magnetite and elemental iron. Write down a balanced chemical reaction for this process.

    (b) some of the magnetite reacts with atmospheric oxygen to give hematite. Write down the corresponding balanced  chemical reaction.

     (c) If cooling is done too rapidly, not all the initial FeO undergoes transformation. Assuming that the various oxides exist as consecutive layers on the steel surface, provide a sketch that clearly shows the oxides representing (i) the inner layer, (ii) the middle layer, and (iii) the outer layer. Justify your selection with appropriate arguments.

Explanation / Answer

A) FeO(s) ? Fe(s) + Fe3O4(s)

To balance Fe, you need 4 Fe on both sides multipl 2*FeO

4 FeO(s) ? Fe(s) + Fe3O4(s)

B)Fe3O4 + O2 ? Fe2O3

To balance Fe, you need 6 Fe on both sides. Multiply 2 * Fe3O4 and 3 * Fe2O3

2 Fe3O4 + O2 ? 3 Fe2O3
8 O

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