Appearance of a negative loop on the polarization curves of Pd₇₈Si₁₆Cu₆-_xCr_x amorphous alloys in phosphate buffered saline solution

As-received and polished Pd₇₈Si₁₆Cu₆-_xCr_x (x= 0-6 at%) amorphous alloys were cathodically and anodically polarized in a deaerated phosphate buffered saline solution. The curves of the as-received alloy showed a region where a cathodic current flowed in the passive region, i.e. a negative loop, after the anodic active region of palladium dissolution. In the negative loop region, a certain surface concentration of silicon and chromium oxide was generated, and proton reduction occurred on the oxide rapidly enough to suppress the anodic reaction. The proton was generated with the anodic dissolution of Pd-H formed in the cathodic polarization region.