Systems, formulations, and methods for removal of diffusion coating from airfoils

Abstract

A method of removing an aluminide diffusion coating from a gas turbine engine component having a nickel alloy base material may comprise: disposing the gas turbine engine component in a solution, the solution including an acid between 5% and 15% vol./vol. and water between 85% and 95% vol./vol.; placing the gas turbine engine component in electrical contact with a graphite plate; and removing the aluminide diffusion coating from the gas turbine engine component in response to placing the gas turbine engine component in electrical contact with the graphite plate and disposing the gas turbine engine component in the solution.

1 . A method of removing an aluminide diffusion coating from a gas turbine engine component having a nickel alloy base material, the method comprising:
 disposing the gas turbine engine component in a solution, the solution including an acid between 5% and 15% vol./vol. and water between 85% and 95% vol./vol.;   placing the gas turbine engine component in electrical contact with a graphite plate; and   removing the aluminide diffusion coating from the gas turbine engine component in response to placing the gas turbine engine component in electrical contact with the graphite plate and disposing the gas turbine engine component in the solution.   
     
     
         2 . The method of  claim 1 , further comprising increasing a reaction rate of the solution in response to generating a voltage differential between the solution and the aluminide diffusion coating. 
     
     
         3 . The method of  claim 2 , further comprising reducing the reaction rate in response to the aluminide diffusion coating being removed and the solution contacting the nickel alloy base material. 
     
     
         4 . The method of  claim 1 , further comprising heating the solution between 80° F. (27° C.) and 140° F. (60° C.). 
     
     
         5 . The method of  claim 1 , wherein the gas turbine engine component includes an airfoil. 
     
     
         6 . The method of  claim 1 , further comprising placing the gas turbine engine component in direct contact with the graphite plate. 
     
     
         7 . The method of  claim 1 , further comprising electrically coupling the gas turbine engine component is electrically coupled to the graphite plate. 
     
     
         8 . The method of  claim 1 , wherein the acid is nitric acid. 
     
     
         9 . A method of removing an aluminide diffusion coating from a gas turbine engine component having a nickel alloy base material via a coating removal system, the method comprising:
 enhancing, via the coating removal system, a reaction rate of a diluted acid solution in response to generating a localized redox reaction between the aluminide diffusion coating and the diluted acid solution;   removing, via the coating removal system, the aluminide diffusion coating from the nickel alloy base material in response to generating the localized redox reaction; and   reducing, via the coating removal system, the reaction rate of the diluted acid solution in response to the aluminide diffusion coating being removed.   
     
     
         10 . The method of  claim 9 , wherein a first electromotive force produced during the enhancing the reaction rate of the diluted acid solution is greater than a second electromotive force produce during reducing the reaction rate of the diluted acid solution. 
     
     
         11 . The method of  claim 9 , wherein the diluted acid solution is an acid between 5% and 15% vol./vol. and water between 85% and 95% vol./vol. 
     
     
         12 . The method of  claim 11 , wherein a temperature of the diluted acid solution is between 80° F. (27° C.) and 140° F. (60° C.). 
     
     
         13 . The method of  claim 12 , wherein the acid is nitric acid. 
     
     
         14 . The method of  claim 9 , wherein the coating removal system includes a graphite plate in electrical communication with the gas turbine engine component. 
     
     
         15 . The method of  claim 14 , wherein the graphite plate is disposed in the diluted acid solution. 
     
     
         16 . A system for removing an aluminide diffusion coating, the system comprising:
 a diluted nitric acid solution comprising nitric acid between 5% and 15% vol./vol. and water between 85% and 95% vol./vol; and   a graphite plate disposed in the diluted nitric acid solution, the graphite plate configured to be in electrical communication with a gas turbine engine component during removal of the aluminide diffusion coating.   
     
     
         17 . The system of  claim 16 , further comprising a heater, wherein the heater is configured to heat the diluted nitric acid solution to a temperature between 80° F. (27° C.) and 140° F. (60° C.). 
     
     
         18 . The system of  claim 16 , further comprising the gas turbine engine component disposed in the diluted nitric acid solution, the gas turbine engine component comprising a base material and the aluminide diffusion coating, the base material comprising a nickel-based superalloy. 
     
     
         19 . The system of  claim 18 , wherein a reaction rate of the diluted nitric acid solution is increased in response to an electromotive force generated from a voltage differential between the diluted nitric acid solution and the aluminide diffusion coating. 
     
     
         20 . The system of  claim 19 , wherein the reaction rate of the diluted nitric acid solution is decreased in response to the aluminide diffusion coating being removed.