Post on 10-Mar-2018
transcript
Starter:
• Rusting of iron or steel needs two things: ____________ and ___________
• The colour of rust is ______________
• The chemical name for rust is ___________
• Which metals can rust?
©cgrahamphysics.com 2016
Aim
• Describe how rusting can be prevented
Keywords
• Galvanization
• Rust prevention
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Starter: explain you experiment
Fill in the results section on your own sheet
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Rusting
Salt speeds up the rate at which iron rusts
iron + oxygen + water hydrated iron oxide
Photo of a rusty pier
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Preventing rust
• Stainless steel
• Protects under normal conditions
• It is expensive
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Galvanizing
• A protective layer of zinc is added on the iron object
• Zinc is more reactive than iron and will corrode away before the iron rusts
• Galvanizing is expensive
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Protective coating
• Paint, grease, plastic and unreactive metals can be applied to the surface of the iron
• It prevents water and oxygen to reach the iron or steel surface
• Protective coating varies in cost
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Question 1:
The paint prevents oxygen and water getting to the iron.
Painting is much cheaper than the alternatives.
It is like painting the Forth Rail Bridge ©cgrahamphysics.com 2016
Question 2:
Chromium is used to stop water and oxygen from reaching
the iron. It is also shiny which looks nice in bathrooms.
Question 3:
It is much cheaper to make the can out of iron and then cover
it in tin to stop it from rusting
Question 4:
Zinc is more reactive than iron so it reacts first – before the
iron – with oxygen and so stops the iron rusting.
Preventing rusting - answers
©cgrahamphysics.com 2016
New products that contain iron are often boxed with a small
packet of drying agent.
Oiling – oil prevents the air or water to reach the iron or
steel
Preventing rusting
The drying agent absorbs any water that may cause rusting.
©cgrahamphysics.com 2016
Plenary: 3, 2, 1
3. When you think of Rusting what three words come to mind?
2. What 2 questions would you like to ask about Rusting?
1. Write 1 simile or metaphor for Rusting
©cgrahamphysics.com 2016
Key words
• Galvanization - is the process of applying a protective zinc coating to steel or iron, to prevent rusting
• Rust prevention - Surface protection of iron structures or equipment to prevent formation of iron oxide; can be by coatings, surface treatment, plating, chemicals, or other means
©cgrahamphysics.com 2016