Preserving a wielded corpse without tinning
You can prevent rotting by storing a corpse in an ice box or slow rotting by leaving it on an ice square, but that's hardly conducive towards you using it as a weapon. There are very few options open if you want to be able to keep your cockatrice corpse as a usable weapon.
One thing you can try, though, is to reanimate it every now and then, kill it again, and hope it drops a fresh corpse.