2020 年 54 巻 135 号 p. 2-
It is well known that electrochemical machining (ECM) of Cr-containing materials such as stainless steel produces hexavalent chromium, which is often taken up as a problem in electrolytic processing. In this study, using the relationship among the standard electrode potential, we investigated whether the formation of hexavalent chromium itself could be suppressed during ECM and developed the method of using divalent iron ions in the electrolyte. If the electrolyte contains many easily oxidized ions, it can be considered that the oxidation of trivalent chromium is prevented by the oxidation of these ions. To supply divalent iron ions to the electrolyte, an iron-ion supply device composed of iron chips was fabricated. It was clarified that the electrolyte must be kept non-alkaline to contain a large amount of iron ions and that with a sufficient amount of divalent iron ions, the formation of hexavalent chromium can be suppressed.