Named after the first Greek gods, the Titans, titanium is prized for its corrosion resistance, strength and high performance at elevated temperatures. It has extremely good strength to weight, superior to most other metals. 7000 series aluminium alloy and nickel Incoloy come close, and some alloy steels are stronger for their weight, but much heavier.

It is expensive because a lot of energy is required to produce the raw material as well as convert it into products. It is produced using the several methods, with the most common being the Kroll process. With this process, titanium is extracted from its ore through a series of high temperature reactions. As a result, it tends to be restricted to the most demanding applications, such as in aerospace, manufacturing, marine and sports.

Pure titanium has exceptional corrosion resistance combined with relatively good formability. They are utilised in aerospace, marine and industrial applications, but are also suitable for medical implants such as to repair broken bones. Their properties differ as a result of the very slight differences in oxygen, carbon and nitrogen.

Titanium is alloyed, such as with aluminium (Al) and vanadium (V), to enhance formability and resistance to creep. A range of alloys exist, which have evolved around the needs of different industries and applications. There are three main classes:
– Type 1, alpha (α) titanium alloys are non-heat-treatable (like pure grades), have moderate strength and good ductility, even at very low temperatures. The can be welded with good results and have very good resistance to corrosion.
– Type 2, alpha-beta (α-β) titanium alloys are heat-treatable. This means they can be formed in their annealed state and then aged to reach significantly higher strength, stiffness and hardness. The most popular is grade 5 Ti 6-4, which accounts for around half of all titanium produced.
– Type 3, beta (β) titanium alloys have good forgeability and generally higher resistance to creep than alpha-beta types. They too can be heat-treated to achieved exceptional strength and hardness.

When exposed to the atmosphere, the surface of titanium oxidises to form a layer of titanium dioxide (TiO2). This layer has very good biocompatibility, stability even at high temperature, and low solubility in water. Furthermore, it improves the wear resistance of the substrate.

Titanium anodising is an electrolytic finishing process that enhances the TiO2 layer on the surface to produce much more durable parts, which are able to resist corrosion from salt water and humidity. It is used to prepare titanium for harsh environments in aerospace, marine and medical applications. By building up the thickness of the oxide layer it is possible to produce coloured finishes. This is used for purely decorative purposes, such as in jewellery and sports equipment, as well as for technical applications such as to aid quick visual identification of parts in medical or aerospace. The colour is the result of light interference and so can change depending on the lighting conditions and angle of view. Thickness determines the colour, from bronze through green.