日本金属学会誌

J. Japan Inst. Metals, Vol. 43, No. 12 (1979),
pp. 1186-1190

Effects of NaClO3 and NaCl on the Corrosion Behaviours of Iron-Chromium Alloys in Hot Concentrated Caustic Soda Solution

Takashi Sakaki1 and Kazutaka Sakiyama1

1Development Laboratories, Toyo Soda Manufacturing Co., Ltd., Yamaguchi

Abstract:

Effects of NaClO3 and NaCl on the corrosion behaviour of iron-chromium alloys are studied by means of potentiodynamic polarization and immersion tests in 48%NaOH solutions at temperatures between 140 and 200°C, and the following results are obtained. With increasing chromium content in alloys, the passivation of iron-chromium alloys even takes place in caustic soda solutions containing small amount of NaClO3 and the dissolution at active state of the alloys containing more than 18%Cr disappears. Natural electrode potentials of alloys that is 24%Cr or less are about Eh=-0.9 V. But, when 0.1%NaClO3 is contained in solution, the corrosion potential of a 18%Cr-Fe alloy shows a high potential in the passive state. Therefore, we suppose that the effect of NaClO3 on the corrosion behaviours is caused by the oxidation power of ClO3- ion. On the other hand, the corrosion of Fe-Cr alloys is invariable in 48%NaOH solutions containing NaCl that is up to 1%. At temperatures more than 160°C, high chromium-iron alloys that have a excellent corrosion resistance at 140°C are corroded. Especially, these alloys are severely attacked in solutions containing NaClO3.


(Received 1979/06/11)

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