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Titanium

*Please note: If you’re interested in working with Titanium, please call to discuss project details. Although we do not keep samples of this material on hand, we are happy to customize based upon your project’s needs.

Titanium was discovered in Cornwall, Great Britain in 1791, and it is named for the “Titans” described in Greek Mythology. In the 20th century the material became used in rocketry and aviation. Thanks in large part to architect Frank Gehry, the metal titanium has undergone a transformation into one of the most formidable architectural metal surfaces. The Guggenheim in Bilbao was the first use of titanium sheathing as an architecture material in 1997. Since then architectural titanium has been used on a number of buildings.

Titanium is almost always provided with the surface finish obtained at the mill. This surface can be a smooth, slightly glossy gray tone or it can be moderately coarse from glass-bead blasting or shot peening. The stiffness of the surface resists deep embossing but can receive many of the same patterns available on stainless steel.

Titanium needs to be viewed in the full spectrum of light. On close examination, the surface looks gray; but at a distance of a few meters, when viewed in the full spectrum, it has a very slight golden cast. On overcast days, the metal looks medium gray with a slight golden tone. On bright sunny days, the gold tone shimmers like nickel silver.

Color spectrum of available finishes on color-titanium. As voltage is increased, thickness of oxide layer also increases

IMAGE © A. ZAHNER COMPANY

COLORING OF TITANIUM SHEETS

Titanium, when subjected to a voltage of sufficient order while immersed in a strong electrolyte, will grow a thick, transparent oxide film. As the film thickens by just a few molecules, colors shift across the spectrum through light interference. For instance, at 10 volts, an 18 picometer-thick (there are a billion picometers in a millimeter) film develops. Pale gold in appearance, this is nearly twice the oxide thickness that develops naturally on the surface of titanium sheet. As the voltage is increased, the color changes from golds to violets, blues, oranges, reds, and greens — all across the color spectrum, albeit pastel in tone.

Titanium can be expected to remain consistent in color for decades, as it has a high resistance to compounds in the atmosphere that can discolor the surface. Discolored titanium, when it occurs, is usually due to the formation of titanium carbide, TiC, below the surface of the oxide. This should not occur under most applications. It can, however, be generated from the mill process. The appearance is a dull, blotchy reflectance in relation to surrounding surfaces of titanium. Interference colors are unique for titanium and differ significantly from the colors produced from stainless-steel interference coloring, and also differ from the possible colors in titanium-coated stainless steel (see below).

TITANIUM COATINGS ON STAINLESS STEEL

Thin films of titanium can be coated on stainless steel sheets through vapor deposition techniques. Vapor deposition is a process whereby a metal film is created on the surface of the metal by vaporizing an alloy of one metal while under vacuum.

Colors available to titanium-coated steels with vapor deposition are limited. The list of colors include black, bronze, light gold, dark gold, rose gold, silver, and grey. Metal coated with this process can be formed without damaging the thin film. Color changes slightly along the bend. The coating is a thin layer of transparent titanium oxide. Stainless steel is the base metal used when achieving the interference colors. The polish on the stainless steel is mirror, satin, angel hair, or any number of mechanically created finishes. The combination of the polish on the base stainless-steel surface with the color achieved by the phenomena of light interference creates different tones, from bright metallic colors to softer, satin finishes.

LONG-TERM PERFORMANCE OF TITANIUM

Titanium is corrosive-resistant and does not react with oxygen or moisture when used as a cladding in rural, urban, or seaside exposures. Of all the metals, titanium is the most inert. Few natural atmospheres will have any permanent effect on the metal. Whether utilized as a cladding near the sea or the industrial center of a city, the metal will stand unaffected and unchanged. Titanium develops a tight, impervious oxide layer immediately on exposure to air. This oxide layer is very thin, less than 10µm (10 micrometers, or 1/100th of a millimeter). This oxide layer will not react with chlorides and sulfides under normal atmospheric conditions.

Mechanical and abraded finishes such as Angel Hair or Glass Bead are rarely applied because of the strange reactive nature of the metal. Titanium has an explosive characteristic when it comes to oxygen. Scratching the surface using sanding belts causes sparks as the minute particles are abraded from the surface. Abrading the surface under oil is dangerous and can cause explosive reactions as the dust finds oxygen. Thus, titanium almost always comes in the mill annealed and pickled state or with a glass bead texture.