Method of controlling the corrosion rate of alloy particles, alloy particle with controlled corrosion rate, and articles comprising the particle

Abstract

A composite particle comprises a core, a shielding layer deposited on the core, and further comprising an interlayer region formed at an interface of the shielding layer and the core, the interlayer region having a reactivity less than that of the core, and the shielding layer having a reactivity less than that of the interlayer region, a metallic layer not identical to the shielding layer and deposited on the shielding layer, the metallic layer having a reactivity less than that of the core, and optionally, an adhesion metal layer deposited on the metallic layer.

What is claimed is: 
     
         1 . A method for adjusting corrosion rate in an aqueous electrolyte of a composite particle having:
 a core;   a shielding layer deposited on the core, and further comprising an interlayer region formed at an interface of the shielding layer and the core, the interlayer region having a reactivity less than that of the core, and the shielding layer having a reactivity less than that of the interlayer region;   a metallic layer not identical to the shielding layer and deposited on the shielding layer, the metallic layer having a reactivity less than that of the core; and   optionally, an adhesion metal layer deposited on the metallic layer,   the method comprising:
 selecting the metallic layer such that the lower the activity of the metallic layer is relative to the shielding layer, the greater the corrosion rate, and 
 selecting the amount, thickness, or both amounts and thicknesses of the shielding layer and metallic layer such that the less the amount, thickness, or both amount and thickness of the shielding layer relative to those of the metallic layer, the greater the corrosion rate. 
   
     
     
         2 . The method of  claim 1 , wherein the interlayer region, shielding layer, metallic layer, and optional adhesion metal layer are inter-dispersed with each other. 
     
     
         3 . The method of  claim 1 , wherein the core comprises magnesium; the shielding layer comprises aluminum, and inclusions of alumina, magnesia, or a combination comprising at least one of the foregoing oxides; and the interlayer region comprises an intermetallic compound. 
     
     
         4 . The method of  claim 3 , wherein the intermetallic compound is γ-Mg 17 Al 12 . 
     
     
         5 . The method of  claim 1 , wherein the metallic layer comprises a group 6-11 transition metal. 
     
     
         6 . The method of  claim 5 , wherein the group 6-11 transition metal comprises Ni, Fe, Cu, Co, W, alloys thereof, or a combination comprising at least one of the foregoing. 
     
     
         7 . The method of  claim 1 , wherein the core comprises an inner core of a first core material and an outer core of a second core material, the inner core material having a lower activity than that of the outer core. 
     
     
         8 . The method of  claim 1 , wherein the inner core comprises aluminum, and the outer core comprises magnesium. 
     
     
         9 . The method of  claim 1 , wherein the core comprises a magnesium-aluminum alloy. 
     
     
         10 . The method of  claim 1 , wherein the core and shielding layer, shielding layer and metallic layer, and metallic layer and optional adhesion metal layer are each in mutual partial contact. 
     
     
         11 . The method of  claim 1 , wherein the shielding layer is cathodic relative to the core and anodic relative to the metallic layer. 
     
     
         12 . A method for adjusting corrosion rate in an aqueous electrolyte of a composite particle having:
 a magnesium-aluminum alloy core;   a shielding layer comprising an aluminum-containing layer deposited on the core, further comprising an interlayer region comprising γ-Mg 17 Al 12  formed at the interface between the magnesium alloy core and the aluminum-containing layer, and further comprising inclusions of alumina, magnesia, or a combination comprising at least one of these oxides;   a metallic layer deposited on the shielding layer, the metallic layer comprising Ni, Fe, Cu, Co, W, alloys thereof, or a combination comprising at least one of the foregoing,   an aluminum-containing shielding layer deposited on the metallic layer; and   optionally, an aluminum-containing adhesion metal layer,   the method comprising:
 selecting the metallic layer such that the lower the activity of the metallic layer is relative to the shielding layer, the greater the corrosion rate, and 
 selecting the amount, thickness, or both amounts and thicknesses of the shielding layer and metallic layer such that the less the amount, thickness, or both amount and thickness of the shielding layer relative to those of the metallic layer, the greater the corrosion rate. 
   
     
     
         13 . The method of  claim 12 , wherein the interlayer region, shielding layer, metallic layer, and optional adhesion metal layer are inter-dispersed with each other. 
     
     
         14 . The method of  claim 12 , further comprising molding a plurality of the composite particles. 
     
     
         15 . The method of  claim 14 , further comprising forging the molded composite particles to form an article. 
     
     
         16 . The method of  claim 15 , wherein the article is a ball, ball seat, or fracture plug. 
     
     
         17 . The method of  claim 12 , further comprising dispersing a plurality of the composite particles in a matrix to form a composition. 
     
     
         18 . The method of  claim 17 , wherein the matrix is non-metallic. 
     
     
         19 . The method of  claim 17 , further comprising applying the composition to a surface to form a coating. 
     
     
         20 . The method of  claim 19 , further comprising performing a controlled electrolytic process on the coating in the presence of water and an electrolyte.