Impedance and transient study of iron and ironphosphorus alloy in carbonate/bicarbonate solution with phosphate anions

✍ Scribed by J. Flis; E. Sikora

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 435 KB
• Volume: 39
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(94)e0029-y

✦ Synopsis

Ano&c oxidation of non and Fe-l 82% P was stu&ed at 75°C m 0 5 M Na,CO, + 1 OM NaHCO, with the addition of 0 5 M and 2 OM Na,HPO, Polanzatlon curves and potentlostatuz transients showed that anodlc currents for the Fe-P alloy were higher than for iron The charge of the active dlssolutlon preceding the onset of passtvatlon was, for the F*P alloy, about four tmes bigger than for Iron, whereas current decays followmg the start of the passivatlon were slower Addition of 2 OM Na,HPO, resulted m an anodic achvaoon of iron slmllar to that caused by phosphorus, demonstrated by higher current of polanzation curves, lllgher mltlal currents at potentials of the passive remon, slower current decays and higher mterfactal capacitance C,, m the active-passive transitIon repon High C,, reachmg 60 F rn-' at the potential of -0 65 V (see), can be ascribed to redox reactions mvolvmg ferrous phosphate and Fe(II1) species It IS suggested that the effect of phosphorus on the anodic behavior of Iron IS associated mamly with the formation of phosphates as a result of oxldafion of phosphorus on the metal surface Key words Iron, Iron-phosphorus, carbonate/bicarbonate, phosphate, capacitance