The Anodic Polarization Behavior of Fe-Ni-P-B and Fe-Ni-Cr-P-B Amorphous Alloys Available to Purchase

The anodic polarization of Metglas™ 2826 (Fe-40Ni-14P-6B) and Metglas 2826A (Fe-36Ni-14Cr-12P-6B) has been studied by standard electrochemical techniques, ellipsometry, and the surface analysis techniques of Auger electron spectroscopy (AES) and electron spectroscopy for chemical analysis (ESCA). The polarization behavior of the Cr-containing alloy suggests a typically passive material. A thin, protective Cr rich film forms at potentials between open circuit (0 mV) and 1000 mV (SCE). At transpassive potentials, Cr dissolution occurs, and the film thickness increases. The apparent active-passive behavior of the Cr-free material appears to be associated with two separate regions of film growth. At more noble potentials, an iron rich film is produced. At more active potentials, the film is nickel rich and much less protective. This behavior is presumably related to the polarization behavior of Ni-P and Fe-P alloys, which indicates that Fe-P can be passivated and Ni-P cannot.