Thin Films of Chromium Electrodeposition from a Trivalent Chromium Electrolyte

SUMMARY

The electrodeposition of thin films of chromium has been investigated under different operating conditions of bath composition, current density, pH and temperature. A detailed study has been made of the influence of these variables on the potentiodynamic polarization curves as well as on the film thickness. The optimum bath composition has been established, it contains: CrCl₃.6H₂O 150, NH₄Cl 50, NaCl 24 and H₃BO₃ 30 g l⁻¹. The optimum operating conditions necessary to produce a firmly adherent chromium thin film have been found to be: pH = 3.5, J = 3 A dm⁻², temp. = 25°C and time = 30 min. The film thickness is greatly sensitive to the operating conditions as well as to the bath composition. X-ray diffraction analysis proved that the Cr deposit under the optimum conditions consists, mainly, of u-chromium and a small amount of γ-chromium.