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trivalent-chromium
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Effects of Additives on Chromium Coating in Trivalent Chromium Bath
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In this work, effects of different additives on trivalent Chromium bath and Chromium coating has been investigated. Malonic acid wich had been used as a complexing agent of the bath improved current efficiancy and coating quality obviously. Effects of Magnesum, zinc, Tin, Aluminium sulfates, Molybdic acid, TiO2 nano particles, Sodium hypophospite, formaldehead and mixtures of these compositions on hexavalent Chromium concentration of the bath were also studied. Concentration of Cr6+ ion decreased by 18 ppm due to adding these materials. Using Ti/ TiO2/ RuO2 Anode also could decrease Cr6+ concentration by 78 ppm. Remarkable results had been recorded in current efficiency and coating...
Electroplating and characterization of Cr–Al2O3 nanocomposite film from a trivalent chromium bath [electronic resource]
, Article Anti-Corrosion Methods and Materials ; Vol 61, No 4, 2014, 205-214 ; Sadrnezhaad, Khatiboleslam ; Salehi Doolabi, Davood ; Sharif University of Technology
Abstract
The main aim of this study was to improve current efficiency and to obtain thicker coatings via aluminum oxide (Al2O3) addition to the chromium (Cr) (III) bath. Design/methodology/approach ‐ Pure Cr and nanocomposite Cr–Al2O3 coatings were electrodeposited from Cr (III) bath onto cathode copper substrates by conventional method. Dependence of current efficiency to current density, Al2O3 content and particle size were investigated. Findings ‐ Current efficiency increased with Al2O3 amount and decreased with Al2O3 particle size. Maximum current efficiency was achieved at 25 A/dm2 for pure Cr and 30 A/dm2 for composite coatings. Al2O3 bath content, current density and stirring rate increased...
Influence of pulse parameters on electrocodeposition of Cr-Al2O3 nanocomposite coatings from trivalent chromium bath
, Article International Heat Treatment and Surface Engineering ; Volume 6, Issue 4 , December , 2012 , Pages 178-184 ; 17495148 (ISSN) ; Sadrnezhaad, S. K ; Salehi Doolabi, D ; Asadirad, M ; Sharif University of Technology
2012
Abstract
Cr and Cr-Al2O3 coatings were electrodeposited from Cr(III) bath with both pulsating and direct current onto copper substrates. Pulsating current resulted in homogeneous films of higher Al2O3 content and lower particle agglomeration than the direct current. Differences were more tangible at shorter duty cycles and pulse frequencies. Pulsating current improved both microhardness and corrosion resistance. The presence of alumina nanoparticles resulted in greater current efficiency, higher film microhardness and better corrosion resistance. Maximum current efficiency, highest microhardness and densest electrodeposited coatings were achieved at current density of 20 A dm-2, duty cycle of 40% and...
Production of Cr-Al2O3 Nano-Composite Coatings by Electrodeposition
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam (Supervisor)
Abstract
Electroplating is an appropriate method for co-deposition of metallic, non-metallic and polymeric fine particles onto a metal matrix for production of functional coatings. In this study, chromium and Cr–Al2O3 composite coatings are electrodeposited from trivalent chromium bath by using DC and square pulse current. Dependence of the amount of Al2O3 nano-particles trapped into the coatings on the Al2O3 bath concentration, average current density, particle size, agitation rate and type of the current is investigated. These parameters are optimized for the highest co-deposition amount of the Al2O3 onto chromium layer. Optimum values are 20g/l Al2O3, 200 rpm stirring rate and 25A/dm2 current...
Pulse Electrodeposition of Chromium Coating From Trivalent Bath and Studying it’s Properties
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor) ; Dolati, Abolghasem (Supervisor)
Abstract
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...
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...