Titanium (Ti) is a metal with a silvery appearance, known for its corrosion resistance and for having the highest strength-to-density ratio of any metallic element. Titanium is often alloyed with other metals such as iron, aluminum, vanadium, and molybdenum. Laser marking of titanium is easily achieved using either a 10.6 or 9.3 micron CO₂ laser or a 1.06 micron fiber laser. The laser marking process heats the surface of the metal, causing oxidation in ambient air to form a dark, often bluish mark. Laser cutting of titanium foils is possible and produces a grey colored edge.