Methods for cleaning a superalloy substrate having engine deposits on its surface are provided. The method may include applying a permanganate solution onto the surface of the superalloy substrate, and applying a ferric chloride based cleaning composition onto the surface of the superalloy substrate. The ferric chloride based cleaning composition includes ferric chloride and at least one of nitric acid and phosphoric acid, such as within a solvent system (e.g., an aqueous solution including water).