Summary

1. Anodic passive films in chromate solutions of pH 3.9, 7, and 12 have the same complex refractive index which is 2.6 (1-0.12i). These films are chiefly composed of ~-Fe~O3 or F~O4. 2. At the open-circuit potential on iron surface vari-ous films are formed depending on experimental con-ditions. They are composed of iron and chromium hydroxide (index of refraction 1.6-1.7) or a mixture of iron and chromium hydroxides with iron and chro-mium oxides (index of refraction 1.6-1.9, with various adsorption coefficients). 3. The films produced on iron surface with an ini-tially formed oxide in aerated chromate solutions of pH 7 and 12 have the index of refraction of 1.6-1.9 with various adsorption coefficients. 4. The kinetics of iron oxide and iron and chromium hydroxide formation at open-circuit potential is loga-rithmic, and the kinetics of iron hydroxide formation at constant potential is cubic. 5. All films formed in chromate solution have a pro-tective nature. Ackno~vledgmen