Diffusion bonding with a bonding surface coating material

A method of diffusion bonding metal or metal alloy containing workpieces, the method comprising:

• (a) coating bonding surfaces of the metal or metal alloy containing workpieces with a layer of a coating material, wherein the coating material does not comprise dissolved polymers and/or compounds having polymerisable functional groups;
• (b) abrading the coated bonding surfaces formed in step (a) to remove surface oxide, the coating material being in a liquid form,
• (c) removing excess coating material or excess abraded metal or metal alloy containing workpiece material from the abraded, still coated bonding surfaces formed in step (b), and
• (d) diffusion bonding the abraded, still coated bonding surfaces of the metal or metal alloy containing workpieces of step (c) together,
• wherein 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 of the metal or metal alloy containing workpieces under diffusion bonding conditions.