A castable, moldable, or extrudable structure using a metallic base metal or base metal alloy. One or more insoluble additives are added to the metallic base metal or base metal alloy so that the grain boundaries of the castable, moldable, or extrudable structure includes a composition and morphology to achieve a specific galvanic corrosion rates partially or throughout the structure or along the grain boundaries of the structure. The insoluble additives can be used to enhance the mechanical properties of the structure, such as ductility and/or tensile strength. The insoluble particles generally have a submicron particle size. The final structure can be enhanced by heat treatment, as well as deformation processing such as extrusion, forging, or rolling, to further improve the strength of the final structure as compared to the non-enhanced structure.