Oxidation behavior of Ni_xFe₁-_x(OH)₂ in C1^--containing solution

The addition of Ni leads to the formation of protective rust layer on steel and subsequently high corrosion resistance of steel in Cl^- -containing environment. α-FeOOH, β-FeOOH, γ-FeOOH and Fe₃O₄ are formed mainly on steels exposed to Cl^- -containing atmosphere. It is expected that systematic investigation of the effect of Ni(II) on the formation process of each oxide in solution should lead to elucidation of the role of Ni in the formation of anticorrosive oxide layer. This study reports the oxidation behavior of Ni_xFe_1-x(OH)₂ in Cl^- -containing solution at two different pH regions (condition I under which solution pH is allowed to decrease and condition II under which solution pH is maintained at 8) where γ-FeOOH and Fe₃O₄ are predominantly formed, respectively, upon the oxidation of Fe(OH)₂. In the presence of Ni(II) in the starting solution, the formation of Ni(II) doped β-FeOOH with very low crystalline was facilitated and the formation of γ-FeOOH was suppressed with increasing Ni(II) content and with increasing oxidation rate of Fe(II). Ni(II) was found to have Fe₃O₄-suppressing effect under condition II.