Corrosion coating for turbine blade environmental protection

A method for coating a portion of a gas turbine engine blade, the method comprising the steps of:

• providing a gas turbine blade comprising a superalloy selected form the group consisting of nickel-base superalloys, cobalt-base superalloys, iron-base superalloys, and combinations thereof, the blade further comprising:
• an airfoil section having at least an exterior surface;
• a platform section having an exterior surface;
• an under platform section having an exterior surface;
• and
• a dovetail section having an exterior surface, the exterior surface of the dovetail section comprising a shank exterior surface and a serrated exterior surface;
• applying a layer of silicon-modified aluminum composition to a preselected exterior surface selected from the group consisting of the under platform exterior surface, the dovetail shank exterior surface, and combinations thereof, the silicon-modified aluminum composition comprising a silicon and aluminum particulate component and an additional component selected from the group consisting of a fugitive binder component, a liquid carrier component, at least one chromium-containing salt component, and combinations thereof, the silicon and aluminum particulate component comprising:
• from about 10 weight percent to about 20 weight percent silicon and balance aluminum;
• heating the gas turbine blade to a preselected temperature in the range of about 600° C. to about 800° C. in an environment selected from the group consisting of a vacuum and a protective atmosphere;
• holding the temperature of the gas turbine blade at the preselected temperature for a preselected length of time in the range of about 0.5 hours to about 4 hours to diffuse the aluminum and silicon particulates into the preselected exterior surface to form a silicon-enriched diffusion aluminide coating;
• cooling the gas turbine blade;
• and
• cleaning the gas turbine blade.