Chapter 19, Problem 19.39QP

Interpretation Introduction

Interpretation:

Need to briefly explain the role of cadmium coating over steel materials.

Concept introduction:

Electro-chemical interaction of metal with the non-metals present in environment resulted in the deformation of the metal surface is called corrosion.  Generally they are converted from metal state to oxide, hydroxide or sulfides, and found to be more stable in it than pure metal state. In case of uncoated-steel, Fe act as anode and release two and undergoes oxidization to produce ${\text{Fe}}^{\text{2+}}$.  The half-cell reaction for corrosion can be written as follows.

    ${\text{Fe}}_{\left(\text{s}\right)}\stackrel{}{\to }{\text{Fe}}^{\text{2+}}{}_{\left(\text{aq}\right)}\text{+}{\text{2e}}^{\text{-}}$

Generally corrosion was accelerated by warm temperature, water and salts.  In order to protect the metal from corrosion, it has to be coated with paint or metal, which will be more stable in general environmental condition.