Chapter 19.8, Problem 3Q

Interpretation Introduction

Interpretation:

The metals which could serve as the sacrificial anode on a steel-sheathed hull has to be determined.

1. a. Tin
2. b. Silver
3. c. Iron
4. d. Nickel
5. e. Chromium.

Concept introduction:

Corrosion :

It is defined as the destruction of metals or alloys through the chemical and electrochemical changes with surrounding or medium.

The chemical composition of rust is : ${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}{\text{.xH}}_{\text{2}}\text{O}$

Protecting metal surfaces from corrosion:

To prevent the corrosion of metals by painting the metal surface or by allowing a thin oxide film to form called anodic inhibition.

In the corrosion process metals undergoes oxidation to prevent the metal oxidation is to force the metal to become the cathode, instead of the anode in an electrochemical cell is known as cathodic protection.

Example: Galvanized iron.

A sacrificial anode is harder to reduce and redox potential value is more negative.