A method for removing a metal layer comprising the steps of providing a part having a slot, providing a porous metallic cathode comprising a recess bounded by a wall having an outer surface corresponding to the slot, inserting the porous metallic cathode into the slot, introducing an electrolyte into the recess of the porous metallic cathode, and removing a portion of an inner surface of the slot by flowing an electric current between the part and the porous metallic cathode.