Abstract: Electrolytes containing water, at least one organic solvent, and at least one alkali metal phosphate salt can be used for anodizing valve metals prepared from metal powder having a surface area of least 0.35 m.sup.2 /g or 35,000 CV/g. The alkali metal phosphate salt should be relatively insoluble in the organic portion of the electrolyte, but highly soluble in a water solution of the organic solvent. The anodizing electrolytes have relatively high conductivity and are capable of being used at high anodizing currents. The anodic film produced by these electrolytes on valve metals is of substantially uniform thickness, has improved electrical parameters, and requires a shorter stabilization time at voltage.