Which of the following releases metal slowly which gives uniform coating in electroplating

• Electroplating, also known as electrochemical deposition or electrodeposition, is a method of generating a metal coating on a solid substrate by reducing metal cations with a direct electric current. The cathode (negative electrode) of an electrolytic cell is the portion to be coated; the electrolyte is a solution of a salt of the metal to be coated; and the anode (positive electrode) is generally either a block of that metal or another inert conductive substance. An external power supply provides the current.

Dissociation of the complex and ion-ion equilibrium