1988 年 37 巻 413 号 p. 229-234
Corrosion of Inconel 600 (I-600) in concentrated NaOH (1-20M) solutions was studied under various temperatures (50-140°C) and potentials. The solution treated (1050°C, 15min) and sensitized (650°C 10hrs) specimens were used. The results are as follows:
(1) The polarization curves for the both specimens showed no change in electrochemical behavior in various corrosive environmental conditions at 50°C. However, the both specimens showed three peaks at higher temperatures than 50°C. The solution treated specimen showed a slightly low current density in the primary passive region and a slightly high current density in the secondary anodic peak, compared with those of the sensitized specimen.
(2) The films formed on the specimen surface during corrosion tests in 20M NaOH solution at 140°C were made of NiO, Cr2O3 and Fe3O4.
(3) The tests of crevice corrosion of I-600 and carbon steel (S15C) showed that general corrosion took place on the solution treated specimen, but the intergranular corrosion under the oxide films took place and it propagated to the crevice in the sensitized specimen.