Electrochemical and ellipsometric investigations of anodic oxidation and film growth on Fe and Fe + 1.1 wt.%P have been performed at 25-degrees-C in a deaerated borate solution (pH 8.5) with additions of sodium hypophosphite (NaH2PO2), potassium phosphite (K2HPO3) and sodium phosphate (Na2HPO4) at concentrations between 0.01 M and 0.5 M. In the active-passive transition region anodic oxidation of Fe and the Fe + P alloy was retarded by small additions of Na2HPO4 (up to 0.05 M) but was accelerated by larger additions and also by the hypophosphite and phosphite salts at all concentrations. Addition of NaH2-PO2 caused pitting of the Fe + P alloy. In the active-passive region two-layer films grew on the metal surface; the optical constants of inner layers were lower in the presence of P oxyanions, indicating a lower film density. In the presence of the oxyanions the films were usually thicker. The inhibiting effect of phosphate anions at low concentrations may result from pore blocking in the film, whereas the activating effect of all the oxyanions may be due to the formation of soluble complexes, incorporation of P-containing salts and/or an increased water content in the passivating oxide film.