Title: The Electrochemical Behavior of Ni-base Metallic Glasses Containing Cr in H<sub>2</sub>SO<sub>4</sub>Solutions
Abstract:In order to develop alloy resistance in aggressive sulphat ion, the corrosion behavior of metallic glasses <TEX>$Ni_{92{\cdot}3}Si_{4.5}B_{32}$</TEX>, <TEX>$Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$</TEX> and...In order to develop alloy resistance in aggressive sulphat ion, the corrosion behavior of metallic glasses <TEX>$Ni_{92{\cdot}3}Si_{4.5}B_{32}$</TEX>, <TEX>$Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$</TEX> and <TEX>$Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$</TEX> (at %) at different concentrations of <TEX>$H_2SO_4$</TEX> solutions was examined by electrochemical methods and Scanning Electron Microscope (SEM) and X-ray Photoelectron Microscopy (XPS) analyses. The corrosion kinetics and passivation behavior was studied. A direct proportion was observed between the corrosion rate and acid concentration in the case of <TEX>$Ni_{92{\cdot}3}Si_{4.5}B_{32}$</TEX> and <TEX>$Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$</TEX> alloys. Critical concentration was observed in the case of <TEX>$Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$</TEX> alloy. The influence of the alloying element is reflected in the increasing resistance of the protective film. XPS analysis confirms that the protection film on the <TEX>$Ni_{92{\cdot}3}Si_{4.5}B_{32}$</TEX> alloy was NiS which is less protective than that formed on Cr containing alloys. The corrosion rate of <TEX>$Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$</TEX> and <TEX>$Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$</TEX>. alloys containing 7% and 13% Cr are <TEX>$7.90-26.1{\times}10^{-3}$</TEX> mm/y which is lower about 43-54 times of the alloy <TEX>$Ni_{92{\cdot}3}Si_{4.5}B_{32}$</TEX> (free of Cr). The high resistance of <TEX>$Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$</TEX> alloy at the very aggressive media may due to thicker passive film of <TEX>$Cr_2O_3$</TEX> which hydrated to hydrated chromium oxyhydroxide.Read More