ギ酸溶液中における高純度金属クロムの耐食性

抄録

Cr is widely used as an essential alloying element for various stainless steels and alloys. Metalic Cr has poor workability in itself and therefore scarcely be used. Recently the high purity Cr sheets have been developed by the improved processing techniques such as electolytic winning, powder refining and rolling, so that various types of sheets and pipes can be fabricated. However, the corrosion behaviour of pure Cr has not yet been completely investigated.
The corrosion behaviour of 99.83%Cr compared with Fe-Cr alloys and Ti was investigated by measuring the polarization curves and corrosion rates in various formic acid solutions. The repassivation rate was measured using the potential pulse method in order to investigate the stability of the surface films.
Cr showed a large value of active dissolution current in formic acid solutions, but its passive current density was very small. And the repassivation rate of Cr was higher than the other materials. Cr had much better corrosion resistance in formic acid solutions than Ti and other Fe-Cr alloys. The corrosion behaviour of Cr depended on the formic acid concentration. On the other hand, the formic acid concentration exerted a greater influence on the corrosion behaviour of Fe-30Cr alloy than Cr. The Fe-30Cr alloy did not show any repassivation ability in various formic acid solutions except the low concentration and low temperature conditions.