The battery cap is corroded on. How can it be removed?

Thanks for the great info! I was about to take my keyboard into a shop to get fixed but found this thread. I used the water-nickel approach and was able to open the sealed cap in a few minutes (after trying to pry it open for nearly half hour with a screw driver and keys yesterday). Inside was two corrosive 2A’s.

God bless you all. Apple keyboard now back in working condition again.

if u have a cook-top stove turn it on high then set the end of the keyboard on the end to get it hot just a few minutes then try to unscrew it after its hot enough if the slot is all tore up from trying u can drill two holes on either side of the cap and then use two small punches or whatever u have to twist it out…not an easy job but it is doable with a little patients…good luck !!

Don't use "good quality" batteries. There are no "good quality" alkaline cells. They all leak, giving you what you have here. Get nickel metal-hydride (NiMH) cells and a smart charger. You probably will want high quality low self-discharge NiMH, like the Sanyo (now Panasonic) eneloop. I've used those for the last ten years and have had zero failures.

In principle, NiMH can leak, too, but I've never seen it or heard of anyone who has. I've been using them exclusively for the last 15 years with no damage to equipment, saving a few hundred bucks along the way. I do have a collection of sometimes expensive equipment destroyed by alkalines before I got wise.

There are other advantages, including both cost and performance advantages, from using NiMH, but this one tops the list.