Silicone lubricant will help the key slide out easily and since it is water resistant it will help to protect your lock against rust.
How to get broken key out of door lock.
If it broke at the head you must get a screwdriver to turn the lock back into position to allow the key to slide back out.
Try to grip the broken key and pull it out.
Mandlebaum says nail clippers or tweezers will grab it just as well in a pinch.
Your main concerns should be the thickness of your tweezers and how far the broken key is in the lock.
Select a silicone spray.
Start by spraying your penetrating oil of choice wd 40 or something like it into the lock to help loosen the broken key.
If the key is sticking try crushing a tiny piece of pencil graphite onto a piece of paper and blowing it into the lock to smooth the way.
Pull the broken key towards you as far as you can using this method then use pliers to pull it from the lock.
When a key breaks off in the lock most people go right for the tweezers.
Most tweezers are inappropriately sized for this task and will just end up pushing the key farther into the keyway.
Insert the tip of a pair of needle nosed pliers into the keyhole.
Place the straw attachment on the spray nozzle.