The free energy change is calculated for the interaction of 19 different oxyanions (metalates) with iron (steel) or aluminum surfaces. The oxyanions considered here are those of the transition metals in the fourth through sixth periods of the periodic table. The oxyanions which produce more negative values of Delta G (o) (per mole of oxyanion) than that of chromate (CrO4 (-2)) are permanganate (MnO4 (-)), nickelate (NiO4 (-2)), ruthenate (RuO4 (-) or RuO4 (-2)), and rhodate (RhO4 (-2)). The oxyanions which produce values of Delta G (o) (per mole of oxyanion) similar to CrO4 (-2) are osmate (OsO4 (-2)), and iridate (IrO4 (-2)).