The sirenic hauberk lasts for 100,000 charges of combat before degrading to nothing - it cannot be repaired. Once equipped, it instantly becomes untradeable, even if it has not been used in combat.
Losing the sirenic hauberk by being killed in the Wilderness will result in a fraction of the original sirenic scales being dropped on death, based on how degraded it was, rounded down. For example, if the hauberk had 52% of its charges remaining, 21 sirenic scales would be dropped on death. This can be used to refund most of the cost of the hauberk, although the algarum thread is not returned.