Nickel corvette is an unofficial designation for the smallest type of Syndicate warship. Smaller than Syndic Hunter-Killers, the ships are so-nicknamed due to their easy dispensibility, similar to the coin of the same name, as described by Captain John Geary, "They're useful, but they don't last long if you need to use them."
He later elaborated that they were cheap, expendable, and considered obsolete even 100 years ago. This inadequacy was made clear when two of these obsolete vessels were faced with newer Alliance combatants in the Corvus system. One was promptly destroyed, and the other surrendered.
Though Geary remarked that the vessels were considered obsolete at the start of the war, a sizable contingent of the Syndicate Mobile Defense Force assets dedicated to the first strike on Alliance shipping moving through Grendel Star System were 'nickel' corvettes. It is possible that Geary's later derision as the fleet moved through Corvus Star System is attributable to inter-fleet rivalry, or a lack of knowledge surrounding Syndicate doctrine at the time.