弱アルカリ溶液中におけるコバルトアノード酸化反応に及ぼすアンモニアの効果

概要

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The anodic polarization curve of cobalt in borate solution is divided into four potential regions: active dissolution, primary passivation, transpassivation, and secondary passivation. These regions remain almost unchanged, whereas the current density increased with ammonia concentration, probably due to the formation of cobalt ammine complex of high solubility, especially in the active dissolution region.Oxyhydroxide and/or oxide deposition occurred on the metal surfaces at potentials more positive than ca. -0.5V vs. Ag/AgCl. In solutions containing ammonia, these oxide layers combined with ammonia to form a cobalt oxide ammonia complex as the reaction intermediate, and then dissolved at an accelerated rate that was dependent on the ammonia concentration.
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