Abstract

A series of polarization and immersion tests on iron-chromium alloys with varing chromium contents were carried out in 48%-NaOH solution at various temperatures and the results obtained are summarized as follows.(1) The dissolution at acitive state decreases with increasing chromium content in alloys and does not occur when the chromium content is over 13% at 100°C and 24% at 140°C. (2) On increasing chromium content, the dissolution as FeO2− ion decreases. (3) At higher potentials, chromium in alloys easily dissolves as CrO42− ion and have no effect to inhibit the dissolution of iron in alloys. (4) Natural electrode potential of alloys containing up to 13%Cr are about Eh=−0.9 V. At 140°C, the natural electrode potential of a 18%Cr-Fe alloy shows a low potential of active state. (5) The corrosion rate logarithmically increases with increasing temperature. (6) The corrosion resistance severly increases with increasing Cr content over 25%. Especially, a 30%Cr-Fe alloy shows excellent resistance.

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