Corrosion in Materials Science

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Questions and Answers

What type of corrosion occurs at the grain boundaries of a metal?

Stress corrosion cracking

Intergranular corrosion (correct)

Localized corrosion

Galvanic corrosion

Which of the following conditions is essential for galvanic corrosion to occur?

Presence of a protective coating

High tensile stress

Contact between dissimilar metals (correct)

Localized corrosion sites

What is a significant characteristic of stress corrosion cracking?

Involves only physical wear and tear

Occurs only at high temperatures

Involves both tensile stress and corrosion (correct)

Requires a lack of moisture

What happens in the anodic reaction during corrosion?

Metal ions are formed Signup and view all the answers

Which of the following examples correctly illustrates galvanic corrosion?

Corrosion of aluminum in contact with copper Signup and view all the answers

What causes localized corrosion in narrow gaps?

Stagnant water trapping Signup and view all the answers

What is often required to detect intergranular corrosion?

Metallurgical analysis Signup and view all the answers

Why does localized corrosion lead to severe damage?

It occurs in isolated areas, leading to significant weakness Signup and view all the answers

In the context of corrosion cells, what occurs at the anode?

Oxidation takes place Signup and view all the answers

What can be done to manage galvanic corrosion?

Separate dissimilar metals Signup and view all the answers

What is the primary cause of corrosion in metals?

Chemical reactions with the environment Signup and view all the answers

Which type of corrosion is characterized by even deterioration across a material's surface?

Uniform corrosion Signup and view all the answers

What type of corrosion occurs in confined spaces where electrolyte flow is restricted?

Crevice corrosion Signup and view all the answers

What is a key characteristic of pitting corrosion?

Formation of deep pits or holes Signup and view all the answers

What is the chemical reaction involved in the rusting of iron?

4Fe(s) + 3O2(g) + 6H2O(l) → 4Fe(OH)3(s) Signup and view all the answers

Which of the following is typically associated with uniform corrosion?

Even deterioration across the entire surface Signup and view all the answers

How does pitting corrosion differ from uniform corrosion?

Pitting corrosion results in deep localized damage. Signup and view all the answers

What factor is a common cause of crevice corrosion?

Stagnant or restricted electrolyte flow Signup and view all the answers

What can result from the effects of corrosion if not properly managed?

Weakened structure and potential failure Signup and view all the answers

Which statement about pitting corrosion is true?

It often leads to significant structural damage. Signup and view all the answers

Study Notes

Corrosion Definition

Corrosion is the deterioration of materials, mainly metals, due to chemical reactions with the environment.

Corrosion Causes

It involves oxidation-reduction (redox) reactions.
Results in material loss, weakening, and potential failure.
General reaction: Metal + Oxygen + Water → Metal Oxide/Corrosion Product
Example: Rusting of iron (4Fe(s)+3O2(g)+6H2O(l)→4Fe(OH)3(s))

Corrosion Types

Uniform Corrosion:
- Even deterioration across the surface.
- Easy to detect and measure.
- Results in gradual thinning.
Pitting Corrosion:
- Localized, deep pits or holes forming on the surface.
- More destructive than uniform corrosion.
- Can lead to perforation.
Crevice Corrosion:
- Occurs in confined spaces or crevices with stagnant or restricted electrolyte.
- Localized corrosion.
Intergranular Corrosion:
- Attacks the grain boundaries of a metal.
- Common in alloys with different phases or impurities at grain boundaries.
- Can lead to material embrittlement and loss of mechanical properties.
Galvanic Corrosion:
- Occurs when two dissimilar metals are in electrical contact with an electrolyte.
- The more anodic metal corrodes preferentially, protecting the more cathodic metal.
- Can be managed by separating dissimilar metals or using protective coatings.
Stress Corrosion Cracking (SCC):
- Results from the combined effect of tensile stress and a corrosive environment.
- Leads to crack formation that can propagate over time.
- Can lead to sudden and catastrophic failure.

Corrosion Mechanisms

Electrochemical reactions occur at the metal's surface, involving oxidation and reduction processes.
Anodic Reaction: Metal loses electrons (oxidation), forming metal ions (M→Mn++ne−).
Cathodic Reaction: Electrons are gained by other species, reducing substances like oxygen or water (O2+2H2O+4e−→4OH−).
Corrosion Cells:
- Different areas of the metal surface act as anodes and cathodes.
- The anode experiences corrosion, while the cathode undergoes reduction.
- Example: Rusting of iron with areas of iron oxidation (anodic sites) and oxygen reduction (cathodic sites).

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Description

This quiz explores the concepts of corrosion, including its definition, causes, and types. Questions will focus on different forms of corrosion such as uniform, pitting, crevice, and intergranular corrosion, highlighting their characteristics and effects on materials. Test your knowledge on how these processes impact engineering and material integrity.