Warning: This is 3.0 Edition material. It is possible that there is more recent 3.5 Edition version.
Inaccurate?

Metal Skin

(Oriental Adventures)

Transmutation
Level: Wu Jen 5 (Metal),
Components: V, S, M,
Casting Time: 1 action
Range: Touch
Target: Creature touched
Duration: 1 minute/level
Saving Throw: None
Spell Resistance: Yes

This spell transforms the skin of the recipient into a gleaming metallic surface.
The recipient's natural armor bonus becomes +8 (unless it was already better than +8), but the creature also becomes somewhat slow and stiff, suffering a -2 penalty to effective Dexterity for the duration of the spell.
Material Component: A small piece of rhinoceros hide.

Also appears in

  1. Complete Arcane