How can I remove corner protectors without damaging the wall?

You will probably expect to do some wall repair, or at leas soem minor paint touch up but its not hard

Try using a heat gun, or if you do not have one, a hair dryer to soften up the glue or tape holding it,

gently and slowly use a slim putty knife to pry the corner off

do not hurry, work slowly for best results

good luck

Sheetrock Corner Protectors

It depends on what the adhesive is made of. Most borders adhesive is water based and so only needs to be saturated with water to the point that it is fluid again, and then it can be wiped up. Steam helps speed this process up. If it is a chemical based adhesive 3M makes some good cleaners that should remove it. Another cleaner that might work is called Goof Off. It works great for most things and if the paintwork is fully cured it should not harm it, assuming you do not apply too much pressure or use something that is too abrasive when rubbing the adhesive off. Check at your local hardware store to find what you need.