Cleaning compositions and methods for removing oxides from superalloy substrates

A method of cleaning a superalloy substrate having engine deposits on its surface, the method comprising:

• applying an alkaline solution to the surface of the superalloy substrate, wherein the superalloy substrate comprises nickel and/or cobalt-containing base metal;
• and
• thereafter, applying an acid solution to the surface of the superalloy substrate, wherein the acid solution comprises a citrate-based organic acid;
• thereafter, applying a permanganate solution onto the surface of the superalloy substrate;
• and
• thereafter, applying a ferric chloride based cleaning composition onto the surface of the superalloy substrate, wherein the ferric chloride based cleaning composition comprises an aqueous solution of ferric chloride, nitric acid, and phosphoric acid.

A method of cleaning a superalloy substrate having engine deposits on its surface, the method comprising:

• applying an alkaline solution to the surface of the superalloy substrate, wherein the alkaline solution comprises sodium hydroxide, sodium gluconate, and a surfactant;
• thereafter, applying an acid solution to the surface of the superalloy substrate;
• thereafter, 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, wherein the ferric chloride based cleaning composition comprises ferric chloride and at least one of nitric acid and phosphoric acid.