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

Abstract As-received and polished Pd 78 Si 16 Cu 6− x Cr 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.