Year 11 Chemistry: Galvanising, Sacrificial Metals & Alloys

Introduction to Galvanising

Galvanising is a process used to protect metals from rusting. Rusting happens when iron or steel reacts with moisture and oxygen in the air. To prevent this, we can coat the metal with a layer of zinc. This coating acts as a barrier, protecting the metal underneath.

How Does Galvanising Work?

1. Zinc Coating: The metal is dipped in molten zinc or sprayed with a zinc solution.
2. Barrier Protection: The zinc layer prevents moisture from reaching the iron or steel.
3. Sacrificial Protection: If the zinc layer gets scratched, it will corrode first before the iron or steel.

Examples of Galvanised Products

• Fences
• Water pipes
• Roofing sheets

Understanding Sacrificial Metals

Sacrificial metals are used to protect more valuable metals from corrosion. They are more reactive than the metal they are protecting. When a sacrificial metal is placed in contact with a more valuable metal, it will corrode instead.

Key Points about Sacrificial Metals

• More Reactive: Sacrificial metals, like zinc or magnesium, are chosen because they react more easily with oxygen and moisture.
• Applications: They are often used in pipelines, ships, and other structures to prevent corrosion of steel.

Example of Sacrificial Protection

Imagine a ship’s hull made of steel. Zinc anodes are attached to the hull. If the ship is in water, the zinc will corrode instead of the steel, keeping it safe.

Introduction to Alloys

An alloy is a mixture of two or more metals (or a metal and a non-metal) that improves some properties of the base metal. Alloys can be made to be stronger, lighter, or more resistant to corrosion.

Key Features of Alloys

• Improved Strength: Alloys are often stronger than pure metals.
• Reduced Corrosion: Some alloys are designed to resist rusting better than their component metals.

Examples of Common Alloys

• Bronze: Made from copper and tin. It is strong and resistant to corrosion, often used in statues and coins.
• Brass: Made from copper and zinc. It is used in musical instruments and plumbing fittings.

Tips and Tricks for Remembering

• Galvanising: Think of zinc as a shield protecting the metal.
• Sacrificial Metals: Remember that these metals “sacrifice” themselves to save others.
• Alloys: Imagine a sports team where different players (metals) come together to make a stronger team (alloy).

Questions

Easy Level Questions

1. What is galvanising?
2. Which metal is commonly used for galvanising?
3. Why do we galvanise metals?
4. What does rusting affect?
5. Name one product that is galvanised.
6. What is a sacrificial metal?
7. Give an example of a sacrificial metal.
8. Why are sacrificial metals more reactive?
9. How does a sacrificial metal protect another metal?
10. Name one alloy.
11. What are alloys made of?
12. Why are alloys often stronger than pure metals?
13. What is bronze made from?
14. What is brass made from?
15. Name a use for bronze.
16. What is the main purpose of galvanising?
17. What happens to the zinc if it gets scratched?
18. How do alloys help in construction?
19. What is the main benefit of using sacrificial metals?
20. What should you remember about galvanising?

Medium Level Questions

1. Explain how galvanising protects metals.
2. What would happen if we didn’t galvanise steel products?
3. Describe the process of galvanising.
4. Why might a ship use sacrificial metals?
5. How does temperature affect the galvanising process?
6. Compare the properties of zinc and iron in the context of galvanising.
7. Explain why bronze is often used for statues.
8. What is the difference between a metal and an alloy?
9. Why is brass used in plumbing fittings?
10. How do alloys change the properties of metals?
11. What are the advantages of using alloys in everyday items?
12. Why is it important to select the right sacrificial metal?
13. Describe a scenario where galvanising would be necessary.
14. How does moisture contribute to rusting?
15. Explain the term “sacrificial anode” in your own words.
16. What are some disadvantages of using pure metals?
17. Why do we use copper in alloys?
18. Discuss how galvanising affects the lifespan of metal products.
19. What role does alloying play in the manufacturing industry?
20. How would you explain galvanising to a friend?

Hard Level Questions

1. Discuss the electrochemical principles behind galvanising.
2. How does zinc corrosion protect underlying steel when galvanising?
3. What are some environmental considerations when using galvanising?
4. Explain the term “passivation” in relation to alloys.
5. Compare the corrosion rates of zinc and iron.
6. How can the choice of sacrificial metal affect the performance of a structure?
7. What scientific principles explain why alloys are often more desirable than pure metals?
8. Describe an advanced application of galvanising in modern technology.
9. How do you test the effectiveness of galvanising?
10. Discuss the economic impact of using alloys in manufacturing.
11. How do alloy compositions change their mechanical properties?
12. Explain the role of metallurgists in developing new alloys.
13. Why might an alloy be preferred in aerospace applications?
14. Discuss the lifecycle of a sacrificial anode in a marine environment.
15. How does galvanising affect the appearance of metal?
16. What happens to the mechanical properties of a metal when it forms an alloy?
17. Describe the role of galvanising in sustainability.
18. How do you determine the reactivity of a metal for sacrificial purposes?
19. Analyze the advantages and disadvantages of using alloys vs. pure metals in construction.
20. Predict future trends in alloy development and their potential uses.

Answers

Easy Level Answers

1. A process to protect metals from rusting.
2. Zinc.
3. To prevent rust.
4. Iron and steel.
5. Fences.
6. A metal that protects another metal from corrosion.
7. Zinc or magnesium.
8. They react more easily with oxygen and moisture.
9. It corrodes instead of the other metal.
10. Bronze.
11. Two or more metals.
12. They combine properties for strength and durability.
13. Copper and tin.
14. Copper and zinc.
15. Statues.
16. To protect from rust.
17. It will corrode first.
18. They are stronger and last longer.
19. It protects the metal from rust.
20. Zinc protects like a shield.

Medium Level Answers

1. It forms a protective layer around the metal.
2. It would rust quickly and deteriorate.
3. Metals are coated with zinc.
4. To prevent the steel from corroding.
5. It needs to be hot for the coating to stick well.
6. Zinc is more reactive and protects iron.
7. It doesn’t corrode easily.
8. Alloys are a mix of metals, while metals are pure.
9. Because it resists corrosion.
10. They can be made stronger and lighter.
11. They are often more durable.
12. To ensure maximum protection.
13. A metal fence exposed to the elements.
14. It causes rusting.
15. A metal that corrodes to protect another metal.
16. They can rust or corrode easily.
17. Copper is strong and conducts heat well.
18. It increases the lifespan.
19. Alloys can be tailored for specific uses.
20. By using simple terms and examples.

Hard Level Answers

1. It involves oxidation-reduction reactions.
2. Zinc oxidises, preventing iron from reacting.
3. Some galvanising methods can release harmful substances.
4. It forms a protective layer on the surface.
5. Zinc corrodes faster than iron.
6. The choice depends on the environment and metal involved.
7. They have specific properties that can be enhanced.
8. In electronics or automotive industries.
9. By checking for rust or coating failure.
10. Alloys can be more expensive but have long-term benefits.
11. Changing the proportion can improve strength or ductility.
12. They create new materials with desired properties.
13. Due to weight and strength requirements.
14. They get worn down over time in saltwater.
15. It can make it look shiny or dull.
16. They can become stronger or more flexible.
17. Reducing waste and increasing durability.
18. Reactivity series can help in selection.
19. Alloys might be more expensive initially.
20. Innovations in materials science could lead to new uses.

Feel free to ask any questions or for further clarification!