I'm not sure what your touch-up is, but if its a standard base coat, it will not adhere to bare metal. Primer adheres to metal, base adheres to primer. Try some primer, available from any auto parts shop.

Its also possible the metal still has wax or other contaminates on, and needs to be cleaned thoroughly. The challenge is to do so without harming the surrounding good paint.

And, finally, the paint - 20-some years old, could just be bad.