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Pulse Electrodeposition of Chromium Coating From Trivalent Bath and Studying it’s Properties

Araban, Vahid | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43777 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad; Dolati, Abolghasem
  7. Abstract:
  8. Trivalent chromium plating has been known as a very promising technology to replace hexavalent chromium which is so toxic. The coatings obtained from tivalent chromium baths have lower thickness and Hardness and higher corrosion rate in comparison with deposits obtained from hexavalent chromium baths.A few studies on pulse plating of trivalent chromium as an effective way to enhance the coating properties have been published.
    In this research glycine was chosen as complexing agent.The results have shown that in pulse plating at 1 Hz, Duty cycle 50%, peak current density 0/2 A/Cm2 and after 30 minutes, thickness achieves 13 µm which is much greater in comparison with coatings obtained in similar conditions with direct current that is 4µm. The passive current density of the coatings obtained in 1Hz, Duty cycle 50% and peak current density 0/2 A/Cm2 is 7mA/cm2, while it’s 65 mA/cm2 in direct current plating at 0/2 A/Cm2. This mentions higher corrosion resistance in pulse plating deposits.The morphology of chromium deposits obtained from glycine baths is a typical nodular structure with micro cracks. Applying anodic currents encourage the grains to grow more nodular and the deposits obtained have more porosity. The deposit is amorphous and has iron and carbon as impurities in its structure. The presence of 48 ppm in fresh bath was confirmed using AAS. UV-visible spectroscopic data shows the Cr(V) generation in bath during plating is in the permissible range.Thus our bath can be used as an environmental friendly bath for chromium plating
  9. Keywords:
  10. Pulse Plating ; Hexavalent Chromium ; Trivalent Chromium Bath ; Glycine ; Chromium Coating ; Environmentally Friendly

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