3.3 Aluminium and Titanium
Aluminium and Titanium are resistant to corrosion. They also have low densities compared with other strong metals.
Aluminium is more reactive then carbon but titanium isn’t ,however reacting it with carbon makes it brittle therefore neither metals can be extracted using their oxides, using carbon.
Pure Aluminium is not very strong, but aluminium alloys are stronger and harder and have many uses.
Both metals are expensive because extracting them involves many stages which requires a large amounts of energy.