Peculiarities of chromium electrodeposition from water − dimethylformamide solutions

Electrodeposition of chromium from both CrCl2- and CrCl3-containing dimethylformamide (DMF)–water solutions is studied. It is found that the process of chromium deposition from Cr(II)-containing solutions is stable during the whole period of electrolysis, while the rate of electrodeposition from Cr(III)-containing electrolytes gradually decreases. To explain the experimental results, it has been assumed that the film consisting of chromium oxide and hydroxide species is formed in the near-cathode region during electrolysis in Cr(III)-based baths. The physical properties of this film are critical for chromium electrodeposition. It is necessary to maintain the negative potential sufficient for Cr(II)→Cr electroreduction at the electrode-film interface for the sustained chromium plating. Under such conditions, thick (up to 100 μm) Cr–C coatings of good quality can be deposited.