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

Potentiodynamic and chronoamperometric polarization measurements, Fe-57 con version electron Mossbauer spectroscopy, X-ray diffractometry and electron microprobe measurements were performed on amorphous and microcsrystalline F e-25Ni-25Cr alloys coatings electrochemically deposited at varying times in comparison with a thermally prepared alloy of the same composition. Signif icant differences were found among the Mossbauer spectra of electrodeposite d alloys reflecting differences in the short range ordering of the dominant ferromagnetic phases. The potentiodynamic polarization curves revealed a h igher ability to spontaneous passivation for the more disordered deposit wh ile anodic dissolution was characteristic for the more ordered electrodepos its and for the crystalline thermally prepared alloy. The onset of the pass ivation of amorphous alloy was enhanced either by the decreased anodic diss olution or the increased hydrogen evolution rate. At the early stage of pas sivation, consistent passivation characterization was found both by chronoa mperometric and potentiodynamic curves and by polarization resistance measu rements performed at open circuit potential. (C) 2000 Published by Elsevier Science S.A.