Surface treatment method for nickel-based metallic glasses to reduce nickel release

Abstract

Surface treatment methods for Ni-based metallic glasses are provided that promote passivation and decrease the amount of Ni released when the Ni-based metallic glass is exposed to a saline containing environment.

What is claimed is: 
     
         1 . A method of treating the surface of a Ni-based metallic glass comprising:
 immersing at least a portion of the Ni-based metallic glass in a chemical treatment solution comprising at least one of an acid solution, a chromate solution, or a molybdate solution to produce a surface treated portion; and   removing the surface treated portion from the chemical treatment solution;   wherein the Ni ion release rate from the surface treated portion when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass having the same composition and having been immersed in the saline solution for one day.   
     
     
         2 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , wherein a duration of immersing in the chemical treatment solution is at least 1 minute. 
     
     
         3 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , wherein the temperature of the chemical treatment solution ranges between 10° C. and 80° C. 
     
     
         4 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , wherein the chemical treatment solution is a nitric acid solution, and where the nitric acid concentration is between 5 and 60 volume %. 
     
     
         5 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , wherein the chemical treatment solution is a sodium dichromate solution, and where the sodium dichromate concentration is between 5 and 200 g/L. 
     
     
         6 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , wherein the chemical treatment solution is a disodium molybdate solution, and where the disodium molybdate concentration is between 10 and 100 g/L. 
     
     
         7 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , where the saline solution has a pH of at least 2. 
     
     
         8 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , where the saline solution has a concentration of NaCl of at least 0.1 g/L. 
     
     
         9 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , where the saline solution is selected from artificial saliva and artificial perspiration. 
     
     
         10 . The method of treating the surface of a Ni-based metallic glass of  claim 9 , wherein the Ni ion release rate from the treated portion of the Ni-based metallic glass when immersed in artificial perspiration is less than 0.88 μg/cm 2 /week. 
     
     
         11 . The method of treating the surface of a Ni-based metallic glass of  claim 1 , wherein a mass of Ni ion released from the treated portion of the Ni-based metallic glass when immersed in artificial saliva for one day is less than 35 μg. 
     
     
         12 . A method of treating the surface of a Ni-based metallic glass comprising:
 immersing at least a portion of the Ni-based metallic glass in an acidic first chemical treatment solution;   removing the portion from the acidic first chemical treatment solution;   immersing the portion in a second chemical treatment solution comprising at least one of a chromate solution or a molybdenum solution; and   removing the portion from the second chemical treatment solution to produce a surface treated portion;   wherein the Ni ion release rate from the surface treated portion when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass having the same composition and having been immersed in the saline solution for one day.   
     
     
         13 . The method of treating the surface of a Ni-based metallic glass of  claim 12 , wherein the acidic first chemical treatment solution comprises a nitric acid solution having a concentration between 5 and 60 volume %. 
     
     
         14 . The method of treating the surface of a Ni-based metallic glass of  claim 12 , wherein the second chemical treatment solution comprises a sodium dichromate solution at concentration between 5 and 200 g/L. 
     
     
         15 . The method of treating the surface of a Ni-based metallic glass of  claim 12 , wherein the second chemical treatment solution comprises a disodium molybdate solution at a concentration between 10 and 100 g/L. 
     
     
         16 . A passivated Ni-based metallic glass comprising:
 an inner bulk material portion, and   an outer passive layer portion having an average combined atomic concentration of Cr and Mo greater than the average combined atomic concentration of Cr and Mo in the inner bulk material portion.   
     
     
         17 . The passivated Ni-based metallic glass of  claim 16 , wherein the outer passive layer is amorphous. 
     
     
         18 . The passivated Ni-based metallic glass of  claim 16 , wherein the composition of the Ni-based metallic glass is defined by the formula:
   Ni 100-a-b X a Z b      wherein:
 X is Cr, Mo, Mn, Nb, Ta, Fe, Co, Cu or combinations thereof; 
 Z is P, B, Si, or combinations thereof; 
 a is between 5 and 25; and 
 b is between 15 and 25. 
   
     
     
         19 . The passivated Ni-based metallic glass of  claim 16 , wherein the average atomic concentration of Cr and Mo in the outer passive layer is at least 2% higher than the average atomic concentration of Cr and Mo in the inner bulk material portion. 
     
     
         20 . The passivated Ni-based metallic glass of  claim 16 , wherein the average atomic concentration of P in the outer passive layer is at least 5% higher than the average atomic concentration of P in the inner bulk material portion.