Among the many different nickel alloys that Corrotherm supplies, one of the most popular is molybdenum. This is because adding molybdenum increases the corrosion resistance of nickel in reducing acids, such as hydrochloric acid. In fact, the molybdenum content of a nickel alloy can increase its corrosion resistance in hydrochloric acid by up to 30% compared to its non-molybdenum counterparts.
Molybdenum was first discovered in 1778 by the Swedish pharmaceutical chemist Carl Wilhelm Scheele and then isolated in its metallic state in 1824. However, it took another 100 years before it gained widespread industrial applications, largely because of the difficulty in extracting it from its native ores.
Alloys of nickel with high levels of molybdenum exhibit excellent repassivation behavior and deactivate pit growth in aggressive chloride solutions (Ahn, 1998; Bastidas, 2002; Ilevbare, 2001; Mishra, 2013). In addition, molybdenum enhances the mechanical properties of nickel, especially at elevated temperatures.
A recent study by Marcus et al investigated the surface composition and morphology of dilute molybdenum/nickel alloys using AES and qualitative LEED. Surfaces of Ni73Mo and Ni-Mo-Ni alloys were ion sputtered with varying molybdenum concentrations and then annealed at 670 to 1070 K. After ion sputtering, all samples showed a surface composition enriched in molybdenum, but after annealing at higher temperatures, the Mo enrichment was no longer apparent. XANES spectra of these samples revealed that the lower-energy binding energy of Mo at the surface was shifted down by the higher-energy Ni orbitals, creating an inverse charge transfer between them. These changes were reflected in the LEED patterns, which became (1
