Corrosion - Pharmaceutical Engineering B. Pharm Third Semester PDF Notes



• Introduction to corrosion

• Components of corrosion 

• Factors affecting corrosion

• Classification of corrosion

• Prevention and control of corrosion

Learning objectives

At this pdf we discuss on following topic:

• Explain various components of corrosion

• Discuss the factors affecting corrosion

• Explain types of corrosion

• Distinguish various methods of corrosion

• Discuss methods to prevent corrosion


Corrosion is a natural process, which converts refined metal to their more stable oxide. It may be of physical, chemical or electro-chemical process

It is the gradual destruction of materials (usually metals) by chemical reaction with their environment (chemical terminology- Corrosion)

In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen

Corrosion is the oxidation of a metal due to an electrochemical reaction.

The oxidizing agent is most often O2 (atmospheric corrosion) or H+ (chemical corrosion) or both

Corrosion can also be defined as the degradation of a material due to a reaction with its environment

Degradation implies deterioration of physical properties of the material

Recipe for corrosion

- Active metal

- Water

- Oxygen (atmospheric corrosion)

- Acid (chemical corrosion)

- Salt

- High temperature

Corrosion product: The compound that is formed during corrosion

Corroded: The metal surface that has undergone corrosion

Corrosion media: Generally liquids (mostly aqueous solutions, solids and gases

Dry or Wet type Corrosion

DRY / Chemical Corrosion

WET / Electrochemical Corrosion

Involves the direct attack of dry gases (air and oxygen) on the metal through chemical reactions

Involves the directs attack of aqueous media (strong or dilute, acidic or alkaline) on metal through electrochemical reactions

As a result an oxide layer is formed over the surface

The moisture and oxygen are also responsible

Not very common

Occurs at anodic area and is quite common

Corrosion facts

Factors Affecting Corrosion

Material related factors

Solution pH

Oxidising agents



Surface films

Constituents of the reaction media

Other factors

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