A method of diffusion bonding metal or metal alloy containing workpieces, comprises (a) coating the bonding surfaces of the metal or metal alloy containing workpieces with a layer of a coating material, (b) abrading the coated bonding surfaces to remove surface oxide, the coating material being in liquid form, (c) removing excess coating material or excess abraded metal or metal alloy containing workpiece material from the coated bonding surfaces, and (d) diffusion bonding the coated bonding surfaces of the metal or metal alloy containing workpieces together. The coating material is operable to form a stable barrier on the bonding surfaces of the metal or metal alloy containing workpieces under ambient conditions, and evaporates from the bonding surfaces under diffusion bonding conditions. There is also a bonded workpiece formed using the method of diffusion bonding metal or metal alloy containing workpieces.