Lec 8.1 - Corrosion

Summary of Scientific Concepts and Discoveries Related to Corrosion

Definition of Corrosion: Corrosion is a natural process that leads to the destruction of materials through reactions with their environment. Rusting specifically refers to the formation of iron oxides (Rust).

Spontaneity of Rust Formation: Rust formation is a spontaneous electrochemical reaction characterized by:

• Positive cell potential (E cell).
• Oxidation at the anode (iron releasing electrons).
• Reduction at the cathode (oxygen reacting with H+ ions).

Types of Corrosion:

• Uniform Corrosion: Even Corrosion across a surface; predictable and less dangerous.
• Localized Corrosion: Includes pitting Corrosion (localized holes), crevice Corrosion (narrow spaces), and filiform Corrosion (under coatings).
• Galvanic Corrosion: Occurs between two different metals in contact, leading to accelerated Corrosion of the anode.
• Erosion Corrosion: Accelerated by fluid flow, leading to non-uniform wear.
• Fretting Corrosion: Occurs at contact points between surfaces due to mechanical movement.
• Intergranular Corrosion: Corrosion along grain boundaries in metals.
• Selective Leaching: Corrosion of specific components in an alloy, e.g., zinc leaching from brass.
• Stress Corrosion Cracking: Combination of Corrosion and stress leading to rapid failure.
• Microbial Corrosion: Caused by Biofilms formed by bacteria.

Methods of Corrosion Prevention:

• Cathodic Protection: Using a sacrificial anode to protect a metal structure by directing Corrosion to the anode instead.
• Surface Treatments:
  • Galvanization: Applying a zinc coating to steel or iron.
  • Anodization: Electrolytic process to create a protective oxide layer on metals.
  • Reactive Coatings: Use of insulating or impermeable coatings to suppress electrochemical reactions.
• Use of Non-Corrosive Materials: Such as gold or platinum in electronics to avoid Corrosion.
• Biofilms: Certain bacteria can form protective Biofilms that inhibit Corrosion.

Applications and Examples:

• The Statue of Liberty's Corrosion issues due to copper and iron interaction.
• The Burj Khalifa's rebars protected by titanium mesh sacrificial anodes.
• Use of graphene and super hydrophobic coatings to prevent Corrosion and biofilm formation in food processing.

Featured Researchers and Sources

• The video does not specify individual researchers but discusses general principles and examples related to Corrosion, including applications in engineering and materials science.