The passivity and passivity breakdown of polycrystalline iron is investigated through electrochemical methods complemented with ellipsometry, by employing plain 0.04 M NaOH and saturated Ca(OH)₂ solutions with the addition of chloride salt of concentrations up to 1 M. The comparative results indicate that the initial reactions of Fe(OH)₂ formation at the inner part of the passive layer level (Fe₃O₄) are only slightly influenced by either the cation or the presence of Cl− ion in solution, in contrast to their large influence at the outer part of the passive layer (hydrous FeOOH species) where Fe²⁺/Fe³⁺ redox reactions take place. At high positive potential the breakdown of passivity is also influenced by both Cl− ion and cation present in solution.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas