US Patent 7700154 Selective aluminide coating process

A method for coating internal surfaces of a turbine engine component comprises flowing an aluminide containing gas into passages in the turbine engine component so as to coat the internal surfaces formed by the passages, allowing the aluminide containing gas to flow through the passages and out openings in external surfaces of the turbine engine component, and flowing a volume of a gas selected from the group consisting of argon, hydrogen, and mixtures thereof over the external surfaces to minimize any build-up of an aluminide coating on the external surfaces.