抄録
The polarization behavior of austenitic stainless steels in hot concentrated caustic soda with and without sodium chloride was investigated by means of the potential sweep and the potential step methods. Iron, nickel, chromium, and molybdenum were also examined as reference. The austenitic stainless steels, Types 304 and 316, showed reproducible potential vs. current density curves when the potential sweep was repeated in pure caustic in the potential range between hydrogen evolution and oxygen evolution (ca. -1.3v to 0.6v vs. Hg/HgO). In solutions containing sodium chloride, on the other hand, the current increased greatly due to pitting when anodically polarized beyond the critical potential. Incident on the surface of specimen was well repaired at the protection potential during potential scan in the cathodic direction. The protection potential moved gradually to less noble values as the chloride concentration increased, and the stable region of passivation diminished.
