Question

Which of the following metal has a nonprotective oxide?

(a) Cadmium (CdO2)

(b) Copper (Cu2O)

(c) Chromium (Cr2O3)

(d) Silicon (SiO2)

I have been asked this question in an online interview.

I would like to ask this question from High-Temperature Corrosion topic in portion High Temperature Corrosion of Corrosion Engineering

Answer 1

The correct answer is:

(a) Cadmium (CdO₂)

Explanation:

A nonprotective oxide layer is one that does not effectively prevent further oxidation of the metal beneath it, allowing corrosion to continue. Cadmium oxide (CdO₂) forms a porous and nonprotective layer, which does not act as an effective barrier to further oxidation, unlike other metals such as chromium and silicon, which form protective, stable oxide layers (Cr₂O₃ and SiO₂) that inhibit further corrosion.