Abstract: Blue chromium films prepared by cathodic electrodeposition on Ni substrate in a solutionof CrO₃, H₂SO₄ and H₂SeO₄ have been studied by XPS and electrochemical measurement.Theresults indicated that the blue chromium films were made up of three layers, correspondingto the three steps in deposition: (1)The reduction of an oxide layer (NiOCrOH) to metallicNi and Cr, which made an inner layer of about 120nm in thickness.(2)The reduction ofCr(Ⅵ)and the depositions of Cr, Cr₂O₃ and CrSe, which formed a medium layer of about 250nm.(3)The deposition and absorbtion of Cr(Ⅲ) and H₂SO₄ and its reduced products,which formed an outer layer of about 100nm.

Key words: blue chromium film, cathodic film, XPS, H₂SeO₄, CrO₃, CrSe