Troll Lord Games

In our ongoing campaign (recently converted to C&C from 1E), we were aware that we would be facing an Iron Golem. So, my idea was to toss at the Iron Golem its nastiest opponent--a Rust Monster. Our druid cast Summon Animal, acquired a wolf from the surrounding countryside (just one, more's the pity, as you will see), and when we encountered the expected Golem, our Wizard used a Wand of Polymorph Other to change the wolf into a Rust Monster, which then attacked the Iron Golem. (Our ironmongery-clad Fighters were hustled to the rear of the party for this encounter.)

That's the good news. The bad news is that the Golem whomped the Rust Monster in a single round (the Golem won initiative), sending the carcass of the now-pulped Rust Monster sailing across the room before it had a chance to attack. Having no other animals to polymorph into additional Rust Monsters, we hitched up our figurative britches and defeated the Iron Golem the hard way--melee combat. It was touch and go for a bit, but we triumphed.

Anyway, my first question is: Had the Rust Monster won the initiative roll vs. the Iron Golem (AC30--considerably higher than its 1E counterpart), would it have needed only a Touch Attack vs. AC10, plus any magical bonus the Golem might have had?

Secondary question: What magical bonus (if any) should an Iron Golem have?
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"You don't understand, Beaufingle", said Lungwort cryptically. "You ARE dinner." -- M.M. Moamrath

The AC of the iron golem is a combination of its enchantment and its toughness. However, to touch it, would be AC 10. That said, it is a magical thing (by nature, all constructs are technically magic items,) and should get a save against the rust monster's attack (according to the rust monster, all magical items are entitled a chance to be unaffected). As to what + it would be equivalent to: +3, and that's easy to then follow the RMs normal rules.

Needless, a rust monster vs. iron golem generally results in rust monster victory. Better get lucky with those initiatives, though.