Rusting
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Define Rusting
A slow chemical reaction of IRON with oxygen in the air in the presence of water
True or false Rusting is a form of corrosion
True
Define corrosion
Process where a metal is damaged or weakened by a chemical reaction
True or false All metals corrode to the same extent
False More reactive metals usually corrode faster than less reactive metals
True or false Gold and platinum are considered the least reactive metals
True That is why it is used in jewellery The don’t corrode after many years
How does rust form
When IRON react with oxygen in the presence of moisture (water) Water is needed for the rusting process
What colour is rust
Orange-red-brown colour solid
Info …
The reaction produces a complex compound that contains iron oxide
Why will something rust faster in Cape Town than here in Johannesburg
It is near the cost and there is more water vapour in the air meaning that the combination of water air and iron is more reactive meaning that rust will occur faster
True or false Rust happens faster when there are impurities in the water like salt
True
True or false Rust stops at some point
False Rust is a continues process that slowly eats away at the metal that will later on create holes on the SURFACE and break it down
What ways can we prevent things from rusting
Painting the iron Using the oil Bars protect ships Galvanised iron INCLUDING Chrome plating PUB GIC
Define the method of :Painting iron to prevent rust
When you paint the metal it prevents the metal from coming into contact with water and oxygen in the air for example we paint ships ,bridges ,fences and certain structures to protect them from resting but if it is scratched the metal underneath can start to rust
Define the method of :Using oil to prevent rust
When we apply a layer of oil to prevent rust by repelling water as oil does not mix with water so water does not come into contact with the metal underneath Eg for bicycles
Define the method of :Using bars to protect ships
Ships and pipelines are always in contact with water, so to prevent rust we attach bars of more reactive metal to them ,magnesium alloys and zinc a more reactive than iron the bar corrodes instead of the iron the corrosion of the bar helps the iron stay intact ,the bar slowly dissolves and must be renewed as quickly as possible.
Define the method of :Galvanising iron to prevent rust
The iron is coated with a thin layer of a more reactive metal that protects the iron .Roofs are generally dipped into molten zinc .Even if the surface is scratched the zinc will corrode before iron
Define electroplating
To use electrolysis to cover one metal with a layer of another metal
Define the method of : Chrome plating to prevent rust
It is used to protect steel or iron ,electrolysis is used in a process called electroplating the electrolysis reaction deposits a thin layer of chromiumon the steel . This protects the seal because chromium does not rust it also forms a shiny attractive surface and is therefore often used to produce components of motorbikes and cars