Influence of Cr addition on the electrochemical behavior of Ni –base metallic glasses in HCl
S.T. Arab1, K. M. Emran2*
Received: 07 April 2008; revised version accepted: 13 July 2008
The contribution of Cr concentration on the corrosion resistance of nickel – metalloids glassy alloys (Ni92.3Si4.5B32, Ni82,3Cr7Fe3Si4.5B3.2 and Ni75.5Cr13Fe4.2Si4.5B2.8) was studied by electrochemical methods , SEM and XPS analyses. The corrosion kinetics and passivation behavior was studied . The study also focused on the HCl concentration and its effect on the corrosion rate, passivation ability and pitting susceptibility on nickel base glassy alloys surface. Cr – free alloy has no ability to reach passive stage and continues in active dissolution. The high corrosion resistance of Cr contains alloys is based on the formation of a protective layer on the surface which acts as a diffusion barrier against alloy dissolution. The addition of Cr enhances the corrosion resistance due to spontaneous passivation. The passive film on the Cr containing alloys consists mainly chromium oxyhydroxide.
Keywords: Metallic glasses; Passivity; Role of chromium; Spontaneous passivation; Polarization; EIS; XPS, SEM.