Acta Phys. -Chim. Sin. ›› 1995, Vol. 11 ›› Issue (10): 921-924.doi: 10.3866/PKU.WHXB19951013

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The Effect of Ce4+ Ion on the Electrodeposition of Metallic Chromium

Liu Shu-Lan,Guo He Tong,Tan Qi-Xian,Cheng Dan-Hong   

  1. Department of Applied Chemistry,Tianjin University,Tianjin 300072
  • Received:1994-10-31 Revised:1995-01-09 Published:1995-10-15
  • Contact: Liu Shu-Lan

Abstract:

It is found through experiments that metallic chromium coating with fine grained and compact crystal structure and high lustre degree can be obtained at near room temperatures by addition of 1.2g.L-1 Ce4+ ion in a chromium plating bath containing 200g.L-1 CrO3 and 2g.L-1 H2SO4. As compared with the traditional chromium plating technology, the new technology can decrease the CrO3 concentration in the plating bath by one-fifth, and decrease the operating temperature by about 30 degrees. The results of X-ray diffraction experiments reveal that the electrocrystallization of metallic chromium in the coating is orientated along the (200) crystal plane. Hence, the coating exhibits high degree of lustre. The results of cathodic polarization curve and differential capacitance curve mesearements show that Ce4+ ion can be adsorbed specifically on the cathode surface. This increases the cathodic polarization value and thus makes the rate of nucleation much faster than that of crystal growth, leading to the formation of fine grained chromium coating. Consequently, the lustre degree of the chromium coating is increased.

Key words: Metallic chromium, Electrodeposition, Ce4+ ion, Lustre degree