Rusting grasp

Rusting grasp is a transmutation spell that lets the caster corrode metals and alloys with a touch.

Effects
You corrode iron and iron alloys at a touch. Any iron or iron alloy item you touch becomes instantaneously rusted, pitted, and worthless, effectively destroyed. If the item is so large that it cannot fit within a 3-foot radius (a large iron door or a wall of iron), a 3-foot-radius volume of the metal is rusted and destroyed. Magical metal items are immune to this spell.

You may employ rusting grasp in combat with a successful melee touch attack. Rusting grasp used in this way instantaneously destroys 1d6 points of Armor Class gained from metal armor (up to the maximum amount of protection the armor offered) through corrosion. For example, full plate armor (AC +8) could be reduced to +7 or as low as +2 in protection, depending on the die roll.

Weapons in use by an opponent targeted by the spell are more difficult to grasp. You must succeed at a melee touch attack against the weapon. (See Strike a Weapon, page 136 of the Player's Handbook.) A metal weapon that is hit is instantaneously destroyed. Note: Striking at an opponent’s weapon provokes an attack of opportunity. Also, you must touch the weapon and not the other way around.

Against ferrous creatures (iron golems, for instance), rusting grasp instantaneously deals 3d6 points of damage +1 per caster level (maximum +15) per successful attack. The spell lasts for 1 round per level, and you can make one melee touch attack per round.