Metal Alloys Flashcards
What are gold alloys used for?
jewellery
Why are alloys harder than metals?
atoms in a metal are all the same size so can slip and slide over each other but atoms in an alloy are all different sizes which disrupts the layers making it harder
What is gold measured in?
carats
What is the percentage of gold in 24 carats?
100%
Why is stainless steel used for cutlery?
resists corrosion
What are aluminium alloys used for?
drink cans
When does corrosion occur?
metal reacts with chemicals in the environment
What are the two ways to prevent corrosion?
- surface coating
- sacrificial protection
Rusting equation
Iron + water + oxygen –> hydrated iron oxide
What is surface coating?
applying a layer on top of a metal to stop the metal’s surface from being in contact with the air
What are som of the material used to coat the metal?
- paint
- oil/grease
- plastic coating
- less reactive metal
- oxide layer
What is electroplating?
coating the metal with a less reactive metal
What does aluminium oxide produce?
oxide layer on the surface of the metal which prevents corrosion
What is sacrificial protection?
block of a more reactive metal are attached to ships so the sea water will now corrode the more reactive metal rather than the iron in the steel as the more reactive metal always reacts first
What is galvanising?
if steel has a coating of zinc, the air and water will corrode zinc rather than the steel underneath
