Titanium
Titanium is the aerospace metal par excellence, as strong as steel but nearly half the weight, completely rust-proof, and able to withstand extreme temperatures. It is inside jet engines, spacecraft, the most advanced surgical implants, and some of the most expensive watches in the world.
- Atomic Number2222 protons, 22 electrons
- Atomic Mass47.867 uAbout 48× heavier than hydrogen
- State at Room TempSolidstrong, silvery metal
- Density4.5 g/cm³About 60% of steel density
- Melting / Boiling1667.8°C / 3286.8°CMelts at a high 1,668°C
- Discovered1791William Gregor, 1791
How does titanium's strength-to-weight ratio compare?
Titanium is as strong as many steels but approx. 45% lighter: the best strength-to-weight ratio of all structural metals.
Titanium (4.51 g/cm³) is approx. 60% the density of steel but almost equally strong. That remarkable strength-to-weight ratio makes it the metal of choice whenever weight must be minimised without sacrificing strength.
What is titanium?
Titanium is a transition metal in Group 4 of the periodic table. It has 22 protons and a silvery, lustrous appearance. Unlike iron, titanium is highly corrosion-resistant, it immediately forms a protective titanium dioxide layer when exposed to air, shielding the metal beneath from further attack. This layer means titanium is completely stable in seawater, body fluids and most industrial chemicals. It is also one of the few metals that burns in pure nitrogen.
Titanium gets its name from the Titans of Greek mythology: the powerful, primordial gods who preceded the Olympians. The name was chosen by the German chemist Martin Heinrich Klaproth in 1795 to reflect what he saw as the imposing strength and resistance of the element. The English chemist William Gregor had actually identified it four years earlier in 1791, calling it manaccanite after the Cornish valley where he found the mineral. Klaproth's name stuck.
Where you find titanium
In space
Titanium is widespread in the solar system. Moon rocks brought back by Apollo astronauts contained significant titanium, particularly in the dark volcanic regions called maria. Calcium-aluminium-titanium inclusions are found in some meteorites, tiny grains of material from the very earliest phase of the solar system.
On Earth
Titanium is the ninth most abundant element in the Earth's crust, more abundant than copper, zinc or nickel, but it is always found as an oxide, never as a free metal.
- Rutile and ilmenite. These titanium dioxide minerals are the primary sources of commercial titanium. Major deposits exist in Australia, South Africa, Canada, Norway and India.
- Titanite (sphene). A calcium titanium silicate mineral found in igneous and metamorphic rocks worldwide.
How we use titanium
- Aerospace and aviation. About two thirds of all titanium metal produced goes into aircraft. Jet engine components, airframe structures and spacecraft use titanium for its unbeatable strength-to-weight ratio.
- Medical implants. Hip and knee replacements, dental implants, bone screws and heart valve components are made from titanium alloys. Bone grows directly onto the metal surface, creating a permanent bond.
- White paint (titanium dioxide). Over 90% of titanium production is not metal at all, it is titanium dioxide (TiO₂), the brilliant white pigment used in paint, sunscreen, food colouring and toothpaste. The white of a white wall is almost certainly titanium dioxide.
- Sports equipment. Titanium frames for bicycles, tennis rackets, golf clubs and climbing equipment offer superior stiffness and strength at lower weight than steel or aluminium.
How it was discovered
Titanium was first identified in 1791 by the Cornish amateur mineralogist William Gregor, who found a black, magnetic sand in the Manaccan Valley of Cornwall and noticed it contained an unidentified oxide. In 1795, the German chemist Martin Klaproth independently found the same oxide in the mineral rutile and named it titanium. However, isolating pure titanium metal proved extraordinarily difficult: the pure metal was not produced until 1910, when Matthew Hunter reduced titanium tetrachloride with sodium metal.
Deeper dive: the Kroll process and titanium's reactivity
Pure titanium is surprisingly difficult to produce despite being so abundant. It reacts with nitrogen and oxygen at high temperatures, which means it cannot be smelted like iron in a normal furnace. The Kroll process, developed by Wilhelm Kroll in 1940, converts titanium dioxide into titanium tetrachloride by heating it with chlorine and carbon, then reduces the tetrachloride with magnesium metal in an inert argon atmosphere. The result, a titanium "sponge", is then melted and processed. The complexity of this process is why titanium is expensive despite being common.
Titanium alloys are more important than pure titanium. The most widely used is Ti-6Al-4V (titanium with 6% aluminium and 4% vanadium), which offers an excellent combination of strength, formability and corrosion resistance. It is the workhorse alloy of aerospace, medical implants and sporting equipment. Titanium aluminides, intermetallic compounds, are even lighter and are used in advanced jet engine blades.
Titanium dioxide (TiO₂) as a white pigment has replaced the toxic lead white and titanium white has transformed painting, coatings and cosmetics since the 1920s. It is the most opaque white material known, a thin layer covers surfaces completely. It is also a photocatalyst: ultraviolet light causes TiO₂ to generate radical molecules that break down organic pollutants, bacteria and even some air pollutants. Self-cleaning glass and anti-bacterial surfaces exploit this property.
Titanium is the metal that bridges the gap between lightweight aluminium and strong steel. Moving to 23 protons brings us to vanadium, a colourful metal used to make some of the world's strongest steel.