Electrochemical behavior of electrodeposited strongly disordered Fe-Ni-Cr alloys

Potentiodynamic and chronoamperometric polarization measurements, 57Fe conversion electron Mossbauer spectroscopy, X-ray diffractometry and electron microprobe measurements were performed on amorphous and microcsrystalline Fe-25Ni-25Cr alloys coatings electrochemically deposited at varying times in comparison with a thermally prepared alloy of the same composition. Significant differences were found among the M?ssbauer spectra of electrodeposited alloys reflecting differences in the short range ordering of the dominant ferromagnetic phases. The potentiodynamic polarization curves revealed a higher ability to spontaneous passivation for the more disordered deposit while anodic dissolution was characteristic for the more ordered electrodeposits and for the crystalline thermally prepared alloy. The onset of the passivation of amorphous alloy was enhanced either by the decreased anodic dissolution or the increased hydrogen evolution rate. At the early stage of passivation, consistent passivation characterization was found both by chronoamperometric and potentiodynamic curves and by polarization resistance measurements performed at open circuit potential.