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

As-received and polished Pd78Si16Cu6-xCrx (x = 0-6 at%) amorphous alloys we re 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, afte r the anodic active region of palladium dissolution. In the negative loop r egion, a certain surface concentration of silicon and chromium oxide was ge nerated, and proton reduction occurred on the oxide rapidly enough to suppr ess the anodic reaction. The proton was generated with the anodic dissoluti on of Pd-H formed in the cathodic polarization region. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.