Solvent metal nodules

Formation of pure solvent metal nodules during... 

Since a continuous oxide scale can form on the alloy surface before the formation of internal oxide precipitates, it is reasonable to suggest that the external oxide scale is another important factor in determining the formation of solvent metal nodules. When the internal oxide precipitation forms in the alloy substrate, stresses are generated, volume expansion occurs and the position of the alloy surface moves outward correspondingly. This volume expansion should be constrained by the oxide scale formed on the alloy... 

The formation of an external oxide scale is also an important factor in determining the formation of pure solvent metal nodules on the alloy surface during oxidation. The stresses generated by the internal oxide precipitation in the alloy are the driving force for the formation of these nodules. Under the constraint of the external oxide scale, solvent metal could be pushed out at the weak locations of the oxide scale to form nodules on the surface. 

FIGURE 8.1 2 Deepsea Ventures solvent extraction flowsheet for separation of metals in a manganese nodule leach liquor. From Ref. 11, with permission. 

---