Chapter 18, Problem 37A

Interpretation Introduction

Interpretation: Pure iron corrodes very fast but steel does not corrode fast. Resistance of corrosion of steel needs to be explained.

Concept Introduction: Corrosion is one of the most common phenomena that can be experienced in daily lives. Some iron-made structures at some point are coated with a colored orange or reddish-brown coating. The formation of this layer is a chemical process called rusting which is a form of corrosion.

Answer to Problem 37A

Steel is comprises of Fe, C and other elements like V, Si, Ni, Mn and Cr. Steel forms a thin adherent layer which prevents further corrosion considerably. Metals like chromium, nickel, and tin, also form a thin layer and protect itself from corrosion. Hence, with this strong oxide coat, steel protects itself.

Explanation of Solution

Corrosion is the process through which a metal lose its strength and also its attractiveness. Stainless steel is comprises of Cr and Ni. Some metals like aluminum, Nickel (Ni), Chromium (Cr) are self protecting metals. They react with oxygen and produce an oxide layer covering the surface of the metal. This layer is less reactive and prevents the further oxidation of metal in atmosphere. Iron also forms protective oxide layer but on expose to oxygen and moisture iron leads to the formation of rust.

Conclusion

Corrosion is a spontaneous process in which the metals become a highly stable chemical substance such as oxides, sulfides, hydroxides, etc.