By far the most important use of titanium is in making alloys. It is the element most commonly added to steel because it increases the strength and resistance to corrosion of steel. Titanium provides another desirable property to alloys: lightness. Its density is less than half that of steel, so a titanium-steel alloy weighs less than pure steel and is more durable and stronger.
These properties make titanium-steel alloys particularly useful in spacecraft and aircraft applications, which account for about 65% of all titanium sold. These alloys are used in airframes and engines and in a host of other applications, including armored vehicles, armored vests and helmets; in jewelry and eyeglasses; in bicycles, golf clubs, and other sports equipment; in specialized dental implants; in power-generating plants and other types of factories; and in roofs, faces, columns, walls, ceilings and other parts of buildings. Titanium alloys have also become popular in body implants, such as artificial hips and knees, because they are light, strong, long-lasting, and compatible with body tissues and fluids.
The most important compound of titanium commercially is titanium dioxide (TiO2), whose primary application is in the manufacture of white paint. About half the titanium dioxide made in the United States annually goes to this application. Another 40% of all titanium dioxide produced is used in the manufacture of various types of paper and plastic materials. The compound gives "body" to paper and makes it opaque. Other uses for the compound are in floor coverings, fabrics and textiles, ceramics, ink, roofing materials, and catalysts used in industrial operations.
Yet another titanium compound of interest is titanium tetrachloride (TiCl4), a clear colorless liquid when kept in a sealed container. When the compound is exposed to air, it combines with water vapor to form a dense white cloud. This property make it useful for skywriting, in the production of smokescreens, and in motion picture and television programs where smoke effects are needed.