Titanium-A armor

Titanium-A armor is the most common form of battle plating used by the UNSC on its warships. It is composed of high-grade Titanium-50 that is specially strengthened at the molecular level, which implies alloying with other elements. It is usually greyish in color.

Titanium-A has numerous uses throughout the UNSC due largely to titanium being lightweight and extremely strong, with a high tolerance to heat. Its primary use is armor for ships. UNSC frigates have sixty centimeters of plating on their hull, and UNSC destroyers have up to two meters of plating. It took a new found importance after the beginning of the Human-Covenant War: To contend with the Covenant's plasma weaponry, humans needed armor that would withstand the heat of the directed plasma. Despite its strength and resistance to heat, however, the Titanium-A plating is usually boiled away within seconds on contact with Covenant plasma torpedoes, and does not effectively dissipate the plasma.

The UNSC uses Titanium-A for construction of military bases as well, to make them less susceptible to destruction. Underground facilities such as HIGHCOM Facility Bravo-6, CASTLE Base and Camp Hathcock used Titanium-A armor in their superstructures.

Titanium-A3 armor

Titanium-A3 is a variant of Titanium-A battle plate developed by ONI's Materials Group. Like Titanium-A, it is chemically altered on the molecular level to produce a stronger plate for ship hulls. It has only been noted to be used on the UNSC Infinity, whose hull is composed of 4.9-meter-thick Titanium-A3 battleplate.