3.4 Corrosion of metals

• Chemistry
• Secondary Education
• Age 12,13

Corrosion of Metals

Topic 3 - Metals

10 November 2023

pages 317-319

• Contribution - 4 points
• Cooperation - 3 points
• Output Quality - 3 points

Peer Performance and Involvement

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Learning Goals

• State the conditions required for the rusting of iron and steel to form hydrated iron (III) oxide
• State some common barrier methods, including painting, greasing and coating with plastic
• Describe how barrier methods prevent rusting by excluding oxygen or water
• Describe the use of zinc in galvanising as an example of a barrier method and sacrificial protection
• Explain sacrificial protection in terms of the reactivity series and in terms of electron loss

Reactivity Series

Gold

Na

Hydrogen~

Zinc

Copper

Calcium

Mg

Silver

Carbon~

Iron

Potassium

Aluminium

Silicon

"Please Stop Calling Me A Careless Zebra, Instead Try Learning How Copper Saves Gold."

Recap

Reactions of Metals

Corrosion of Metals

Topic 3 - Metals

10 November 2023

pages 317-319

• Rusting - the corrosion of iron and steel to form rust (hydrated iron (III) oxide)

• Galvanising - the protection of iron and steel objects by coating with a layer of zinc

• Sacrificial protection - a method of rust protection involving the attachment of blocks of metal more reactive than iron to a structure (this metal is corroded rather than the iron or steel structure)

Vocabulary

Independent Learning

Corrosion of Metals

Topic 3 - Metals

10 November 2023

Collaborative Learning

• Gather in groups of 4.
• Read carefully the situation and answer the following questions:

• Q1 - Why might rust on the outside of the can affect the food?
• Q2 - Why would zinc be a good metal for the outside of the can?
• Q3 - Why would zinc be a bad choice for the inside of the can?
• Q4 - Why would tin be a good choice for the inside of the can?
• Tin is the metal now used to coat both the inside and the outside of food cans.
• Q5 - The first cans used lead, which was discontinued even though lead is less reactive than tin. Suggest why.

Corrosion of Metals

Topic 3 - Metals

10 November 2023

Analysis

• Aluminium cans are used for drinks. Suggest reasons why they are not often used for food.

Analysis

• Coating an iron or steel object with zinc is a useful barrier method to prevent rusting. Coating with zinc continues to prevent rusting even if the protective layer is scratched or broken. Why does this happen?

Analysis

• Coating an iron or steel object with zinc is a useful barrier method to prevent rusting. Coating with zinc continues to prevent rusting even if the protective layer is scratched or broken. Why does this happen?

Analysis

• Sacrificial protection requires blocks of metal higher in the reactivity series than iron, as such metals react to form cations more readily than iron. Name another metal that can be used for sacrificial protection.

Analysis

• Write the complete half-equation showing the formation of zinc ions during sacrificial protection.

Corrosion of Metals

Topic 3 - Metals

10 November 2023

Goal Check

• State the conditions required for the rusting of iron and steel to form hydrated iron (III) oxide
• State some common barrier methods, including painting, greasing and coating with plastic
• Describe how barrier methods prevent rusting by excluding oxygen or water
• Describe the use of zinc in galvanising as an example of a barrier method and sacrificial protection
• Explain sacrificial protection in terms of the reactivity series and in terms of electron loss