Surface Enrichment in Fe-Ni Binary Alloys in 1N H2SO4 at 25C

摘要

The dissolution characteristics of high purity Fe-Ni binary alloys were investigated in 1N H2SO4 at 25C. The specimens were dissolved at constant potential Atomic absorption analysis was used to analyze the solutions to determine the Fe and Ni concentrations and their respective rates of dissolution. The dissolution behavior of the alloys was plotted as a logarithmic function of the form c = at(n) where c was the concentration of Fe or Ni, t was time, n was the slope of the logarithmic curve, and a was a constant. The slopes in for all alloys was approximately 1.0, indicating a linear rate of dissolution. Using this approximation to determine intrinsic zero-order rate constants and (Fe/Ni) ratios in solution, enrichment of nickel on the surface of alloys containing 5 to 50 atomic per cent nickel could be expected at high dissolution potentials of O mV(SHE). Anodic polarization curves were determined from weight changes, which correlated well with integrated currents and total ions in solution. Both the corrosion currents and the anodic Tafel slopes changed significantly from the bcc 20 per cent nickel alloy to the fcc 45 per cent nickel alloy. This indicates that these characteristics may be a function of alloy structure. (Author)