Unlike Alloy Z which is built for multiple purposes including armor and weapons, Alloy X is built primarily for offense. It appears to be difficult to produce as Dr. Hell could only create arrowheads. This metal is able to make a clean shot through Alloy Z. However it is less effective against Super Alloy Z, only able to pierce a few meters through the armor.
Dr. Hell designed Alloy X specifically to pierce Alloy Z armor. This metal was used for the construction of Gokyun U5's weapons. After demonstrating its capabilities, the Mechanical Beast was sent against Mazinger Z. Easily downing Aphrodite A, the Alloy X arrows do considerable damage to Z, disabling its heat sink panels. However, with Z overpowering Gokyun, Alloy X ceased further uses.