Abstract: A quasi-single phase or single phase thick platinum nickel aluminide coating and methods for forming the coating over a nickel-based superalloy substrate are provided. The method includes the steps of forming a metal layer over a surface of the nickel-based superalloy substrate, the metal layer comprising platinum, growing a diffusion zone comprising a platinum nickel alloy layer from the metal layer and the nickel-based superalloy substrate, and subjecting the platinum nickel alloy to one or more aluminization cycles to transform the platinum nickel alloy into a platinum nickel aluminide coating having a platinum aluminide phase formed therein.