1980 Volume 46 Issue 12 Pages 1518-1524
The effect of Cr content on high rate anodic dissolution behavior of nickel-based superalloys has been studied. The polarization curves and the dissolution current efficiency were measured with the specimens of Ni-Cr alloys from 0% to 60% Cr in 2M NaCl and 3M NaNO3 solutions at 30°C. The polarization measurements were carried out in static and flowing electrolytes, and the dissolution current efficiency measurements were carried out in flowing electrolyte under controlled current densities ranging from 1 to 100 A/cm2. The alloy containing 10% Cr dissolves in the active state at 100% current efficiency in NaCl solution. In NaNO3 solution, secondary passivation and oxygen gas evolution take place at the potentials above 1.4 V (vs. SCE), then the dissolution current efficiency is only 5-20%. The alloys containing≥30% Cr in NaCl solution and the alloys containing≥20% Cr in NaNO3 solution dissolve in the transpassive state at the potentials above 0.8 V (vs. SCE) and the dissolution current efficiency is about 100%, independent of current density.
