The present disclosure relates to an apparatus and a method for vaporizing a liquid to form vapor preferably in a gas stream. The apparatus includes a composite metal structure, the structure comprising a plurality of passageways for providing heat to vaporize the liquid in the gas stream to form a gas/vapor mixture. A non-corrosive interface lies between the metal structure and the gas/vapor mixture, the interface being chemically inert to the gas/vapor mixture and the structure permitting heat to be conducted rapidly therethrough to vaporize the liquid. The apparatus further includes an inlet for the gas and an inlet for the liquid to be vaporized to flow into the plurality of passageways and an exit through which the gas/vapor mixture exits the apparatus.