Corrosion - Pharmaceutical Engineering B. Pharm Third Semester PDF Notes
Corrosion
Contents
• 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
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)
- 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
• Temperature
• Velocity
• Surface films
• Constituents of the reaction media
• Other factors
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