I believe this is Return of the Living Dead 3.
From the Wikipedia plot outline:
The corpse is exposed to 2-4-5 Trioxin gas, which re-animates the corpse into a zombie. The military hopes to use zombies in combat. However, they are impossible to control as their hunger for human brains causes them to constantly attack.
To deter the zombies' vicious nature, Sinclair suggests permanently attaching the zombies to exoskeletons that will immobilize them when they are not in battle. Reynolds prefers a method referred to as "paretic infusion", which involves firing a chemical projectile into the forehead of the zombie. This causes an endothermic reaction, freezing the zombie's brain and temporarily immobilizing it.
When the paretic infusion method is tested on the zombie in the lab, it is only successful for a few moments, wearing off much faster than expected; the zombie breaks free and attacks a scientist, biting his fingers off before bashing his head against a wall, killing him. Infected by the zombie's bite, the scientist re-animates and attacks another technician. The initial zombie and the reanimated scientist are paralyzed with bullets and the survivors in the room are quarantined. Reynolds is removed from the project and reassigned to Oklahoma City, while Sinclair is promoted to head of the project.
Although the audio is in Spanish, the scene can be seen here: