Methods for cleaning substrates

Abstract

A method for removing sand particles from a substrate is described. The method includes the step of treating the substrate with an acid solution comprising H x AF 6 , wherein A is selected from the group consisting of Si, Ge, Ti, Zr, Al, and Ga; and wherein H x AF 6 is present at a concentration in the range from about 5 weight percent to about 40 weight percent.

1 . A method for removing sand particles from a substrate, comprising the step of treating the substrate with an acid solution comprising H x AF 6 , wherein A is selected from the group consisting of Si, Ge, Ti, Zr, Al, and Ga; and wherein H x AF 6  is present at a concentration in the range from about 5 weight percent to about 40 weight percent. 
     
     
         2 . The method of  claim 1 , wherein the H x AF 6  acid solution is an aqueous solution. 
     
     
         3 . The method of  claim 1 , wherein the concentration of the H x AF 6  acid is in a range from about 10 weight percent to about 30 weight percent. 
     
     
         4 . The method of  claim 2 , wherein the H x AF 6  acid solution is maintained at a temperature no greater than about 100° C. during treatment. 
     
     
         5 . The method of  claim 1 , wherein the substrate is treated with a wetting agent, prior to treatment with the fluosilicic acid solution. 
     
     
         6 . The method of  claim 5 , wherein the wetting agent comprises a surfactant. 
     
     
         7 . The method of  claim 5 , further comprising rinsing the substrate with water prior to treatment with the wetting agent. 
     
     
         8 . The method of  claim 1 , further comprising rinsing the substrate with water after treatment with the H x AF 6  acid solution. 
     
     
         9 . The method of  claim 1 , wherein the treatment with the H x AF 6  acid solution is carried out for a time period in a range from about 10 minutes to about 2 hours. 
     
     
         10 . The method of  claim 1 , wherein treatment with the H x AF 6  acid solution is carried out at a temperature in a range from about 20 degrees Celsius to about 100 degrees Celsius. 
     
     
         11 . The method of  claim 10 , wherein the temperature is in a range from about 50 degrees Celsius to about 80 degrees Celsius. 
     
     
         12 . The method of  claim 1 , wherein the substrate is at least partially immersed in a bath of the H x AF 6  acid solution during treatment. 
     
     
         13 . The method of  claim 12 , wherein the bath is mechanically agitated during treatment. 
     
     
         14 . The method of  claim 5 , wherein the substrate is at least partially immersed in a bath of the wetting agent for treatment, for a period of time in a range from about 10 minutes to about 2 hours. 
     
     
         15 . The method of  claim 1 , wherein the substrate is a section of a turbine engine component. 
     
     
         16 . The method of  claim 15 , wherein the turbine engine component is an airfoil. 
     
     
         17 . The method of  claim 1 , wherein the sand particles have an average particle size in the range of about 0.5 micron to about 10 microns. 
     
     
         18 . The method of  claim 15 , wherein the turbine engine component is formed of a material which comprises a steel, a superalloy, a titanium alloy, or a combination thereof. 
     
     
         19 . The method of  claim 18 , wherein the turbine engine component comprises a shroud, a bucket, a blade, a nozzle, a vane, a diaphragm component, a seal component, or a valve stem. 
     
     
         20 . The method of  claim 18 , wherein the coating comprises CMAS (calcium-magnesia-alumina-silicate). 
     
     
         21 . The method of  claim 1 , wherein at least one protective coating is disposed over the substrate; and the sand particles being removed are those which adhere to a surface of the protective coating. 
     
     
         22 . The method of  claim 21 , wherein the protective coating comprises a diffusion coating or an overlay coating. 
     
     
         23 . The method of  claim 21 , wherein the protective coating comprises an underlying metallic coating, and an overlying ceramic barrier coating. 
     
     
         24 . A method for removing sand particles from a surface of at least one protective coating disposed on a superalloy substrate, comprising the step of treating the coated substrate with an acid solution comprising H x AF 6 , wherein A is selected from the group consisting of Si, Ge, Ti, Zr, Al, and Ga; and wherein H x AF 6  is present at a concentration in the range from about 5 weight percent to about 40 weight percent. 
     
     
         25 . The method of  claim 24 , wherein the protective coating is a thermal barrier coating.