Chapter 19, Problem 19.40QP

Interpretation Introduction

Interpretation:

Need to explain the corrosion resistance of steel coated with tin and zinc, upon scratching and exposing towards electrolyte.

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 Fe²⁺. Generally corrosion was accelerated by warm temperature, water and salts. The half-cell reaction for corrosion can be written as follows.

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

Galvanization and tin coating are much important method used to protect iron from corrosion.