Corrosion

• Chemistry
• Secondary Education

TEMPLATE

Topic 7 - Metals

Corrosion of Metals

17 November 2025

How do you feel today?

😒🙁😐🙂😃

TEMPLATE

• I will know some common methods to prevent iron from rusting.
• I will understand why a galvaniser coats iron or steel with zinc to prevent rusting.
• I will be able to use the terms ions, electrons, and electron transfer to explain why iron dust does not rust when coated with zinc.

TEMPLATE

What is a galvanised iron?

TEMPLATE

What is a galvanised iron?

What is a galvanised iron?

TEMPLATE

Question:

What is rust, and how does it form?

• Colour
• Physical State
• Formation of rust 

TEMPLATE

Corrosion of iron (Rusting)

iron

oxidised iron + water

hydrated iron (III) oxide

oxygen

water

a.k.a. RUST

TEMPLATE

• Simple barrier methods
• Galvanising
• Sacrificial protection

Preventing Rust

oxygen

water

TEMPLATE

Simple barrier methods

oxygen

water

coating

iron (no rusting)

• painting the iron
• coating the iron with oil or grease
• coating the iron with plastic
• coating the iron with a less reactive metal

TEMPLATE

Galvanising

oxygen

water

zinc (serves as the anode)

iron (serves as the cathode)

Zinc is oxidised (corrodes)

e- flow

TEMPLATE

The Chemistry of Galvanisation

zinc

iron

Can the zinc still protect the iron when it has corroded?

TEMPLATE

Sacrificial protection

zinc (serves as the anode)

iron (serves as the cathode)

More reactive metal is sacrificed.

TEMPLATE

Sacrificial protection

magnesium (serves as the anode)

iron pipes (serves as the cathode)

More reactive metal is sacrificed.

wire

e- flow

water

oxygen

TEMPLATE

Scenario:

In an experiment to investigate the rate of steel rusting, three pieces of steel were used. One piece of steel was completely coated with copper, one with zinc, and the third was left uncoated. All three pieces were left exposed to the atmosphere.

          Explain why the uncoated piece started to rust.

TEMPLATE

Work in pairs:

Do Activity 4 - Corrosion of metals in your LAP sheets (Questions 1 to 3)

How well did you enjoy the lesson today?

05