What exactly do "make you vulnerable to this element" curses do?

[RegalStar]

the Lead-Filled Mace 'Erend' (6d3) (-13,+17) <+1> (charging) {!!, cursed}
Dropped by Kavlax the Many-Headed at 2250 feet (level 45)

It makes your skin harder to damage, but conduct electricity.
+1 wisdom.
+1 tunneling.
Slays undead (powerfully), demons (powerfully), dragons, trolls,
orcs, evil creatures.
Branded with weak fire.
Provides resistance to Fire, Chaos.
Cannot be harmed by Acid, Fire.
Grants telepathy. Grants the ability to see invisible things.

When activated, it attempts to magically enhance a weapon's to-hit
bonus.
Takes 418 to 561 turns to recharge at your current speed.
Your chance of success is 28.6%

Combat info:
5.8 blows/round.
Average damage/round: 667.9 vs undead and demons, 496.8 vs
dragons, trolls, and orcs, 411.6 vs evil creatures and creatures
not resistant to fire, and 326.3 vs. others.

Found this thing in midgame and would like to see if I can use it, but I can't remove that curse with storebought scrolls (it's like strength 93 or something) and I have no idea what I'm dealing with on that curse line. In particular, if I find something with iElec will it then be safe to use?

[normkewl]

Increases your armor class, but removes your resistance to electricity. Not sure if you got something that made you immune to electricity would be safe.

[mrfy]

When activated, it attempts to magically enhance a weapon's to-hit bonus.

I'm amused that it's activation could potentially wipe out the -13 to hit. It might take a while to successfully do so, though.

[RegalStar]

I'm amused that it's activation could potentially wipe out the -13 to hit. It might take a while to successfully do so, though.

I tried it and the activation seems like it would always fail when it's used on itself, so I'd still have to stockpile enchant scrolls I find to get rid of it (or maybe find another randart with the same activation)

[backwardsEric]

If you find something with immunity to electricity, that would override the vulnerability. If you have no source of resistance to that element, the vulnerability will cause additional damage (one third more) from that element and will prevent timed effects providing temporary resistance to that element (so you'd gain no benefit from the electrical resistance part of Colluin's activation or a mage's Resistance spell). If you do have a resistance but not immunity to that element, the vulnerability cancels that. You take damage as if you had no resistance at all but could use timed effects that provide resistance to that element.