Abstract: A method comprises the following steps: a) Providing a body having an internal surface which defines an internal pathway within the body, the body having an inlet and an outlet both communicating with the internal pathway; b) Introducing a liquid solution into the internal pathway so as to fill at least a portion of the internal pathway with the liquid solution, the liquid solution comprising a solute capable of undergoing thermal decomposition; c) Heating the liquid solution while the liquid solution fills said at least a portion of the internal pathway to a sufficient temperature so that the solute undergoes thermal decomposition to form a decomposition product within said at least a portion of the internal pathway. The heating step forms a coating comprising the decomposition product on at least a part of the internal surface that borders the internal pathway.