Abstract: A method for preparing a solution for treating an article, a treatment solution made thereby, and a method for treating an article with the solution are presented with, for example, the treatment method comprising providing a quantity of treatment solution, the treatment solution comprising an acid having the formula HxAF6, wherein A is selected from the group consisting of Si, Ge, Ti, Zr, Al, and Ga, and x is in the range from about 1 to about 6; determining a concentration of free acid contaminant in the treatment solution; and removing the concentration of free acid contaminant.

Abstract: An electrode for rejuvenating a cooling passage within an airfoil, the electrode including a tip, an end, a conductive core extending between the tip and the end, and an insulating coating disposed on the conductive core. The insulating coating exposes a number of conductive strips of the conductive core extending between the tip and the end. The insulating coating forms a number of insulating portions and further exposes a number of spacer portions of the conductive core longitudinally positioned between the insulating portions. The insulating portions substantially span a distance between the tip and the end and are positioned between the conductive strips.

Abstract: An electrochemical stripping method for selectively removing at least one coating from the surface of a substrate is described. The substrate is immersed in an aqueous composition through which electrical current flows. The composition includes an acid having the formula HxAF6, in which “A” is Si, Ge, Ti, Zr, Al, or Ga; and x is 1-6. Various coatings can be removed, such as diffusion or overlay coatings. The method can be used to fully-strip a coating (e.g., from a turbine component), or to partially strip one sublayer of the coating. Related processes and an apparatus are also described.

Abstract: A method for selectively removing portions of a diffusion aluminide coating from a substrate is described. The coating is treated with an aqueous composition based on an acid having the formula HxZrF6, wherein x is an exemplary 2. The coating being removed is usually a noble metal-aluminide coating, and the substrate is typically a superalloy. Related compositions are also described.

Abstract: An electrochemical stripping method for selectively removing at least one coating from the surface of a substrate is described. The substrate is immersed in an aqueous composition through which electrical current flows. The composition includes an acid having the formula HxAF6, in which “A” is Si, Ge, Ti, Zr, Al, or Ga; and x is 1-6. Various coatings can be removed, such as diffusion or overlay coatings. The method can be used to fully-strip a coating (e.g., from a turbine component), or to partially strip one sublayer of the coating. Related processes and an apparatus are also described.

Abstract: A method for selectively removing oxide material from the surface of a substrate or coating disposed on the substrate is disclosed. The method includes the step of contacting the oxide material with an aqueous treatment composition having the formula HXAF6, wherein A can be Si, Ge, Ti, Zr, Al, and Ga; and x is 1-6. The composition can sometimes include an additional acid, such as phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, and mixtures thereof. A method for replacing a worn or damaged protective coating applied over a substrate, utilizing the treatment composition, is also described.