• Journal of the Korean institute of surface engineering
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• v.37 no.3
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• pp.179-184
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• 2004

Hard chromium coating technology using hexavalent chromium bath is widely used in various industries. Because of the serious health and environmental problems of hexavalent chromium, many attempts to alternate the hexavalent chromium plating have been made over 50 years. Trivalent chromium plating is one of the challengeable technologies to alternate hexavalent chromium plating. It is relatively none-toxic. Although some papers have described hard chromium coatings produced from trivalent chromium solution, it has limited the industrialization because of chemical and electrochemical problems of trivalent chromium ions. This paper introduces a number of factors for successful trivalent chromium plating, to give a some information about trivalent chromium process.

• Journal of the Korean institute of surface engineering
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• v.30 no.2
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• pp.104-110
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• 1997

Conventional hexavlent chromium electroplating baths deposit the matal at low cathode efficiency and have poor covering and throwing power. The processs also generate hazardous wastes. To overcome many of the disadvantages of hexavalent chromium plating the use of trivalent chromium has advocted. After Yoshida, who first studied trivalent chromium plating, using ammonium sulfate and urea, there are numerous report describing the trivalent chromium electropating process using complexing agents. This study investigaten trivalent chromium plating electrolyte solutious containing formate as a complexing agent and ammouim chloride for conducting agent. The effects of composition and operating conditions on deposits and current efficiencies were investigated in trivalent chromium plating baths by analyzing the relationship pulse conditions and surface morphology The surface morphology of the deposits was observed by SEM. pulse electrolysis has been effective on obtaining a smooth with high current efficiency comparing with D.C. electrolysis in trivalent chromium solution.

• Journal of the Korean institute of surface engineering
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• v.44 no.1
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• pp.7-12
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• 2011

The effect of organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was analysed in the view point of current efficiency, solution stability and metallurgical structure. It was measured that PEG-containing trivalent chromium solution had about 10% higher current efficiency than pure solution and controlled the micro-crack density of electrodeposits. PEG exhibited profound effect on the solution stability by reducing the consumption rate of formic acid which acts as a complexant to lower the activation energy required for electrochemical reduction of trivalent chromium ions. It was also revealed that the formation of chromium carbide layer was facilitated in the presence of polyethylene glycol, which meant easier electrochemical codeposition of chromium and carbon, not single chromium deposition. Trivalent chromium layer formed from PEG-containing solution was amorphous with local nano-crystalline particles, which were prominently developed on the entire surface after non-oxidative heat treatment.

• Journal of the Korean institute of surface engineering
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• v.36 no.2
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• pp.161-167
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• 2003

In order to investigate the effects of pulse plating conditions on the electrodeposition of trivalent chromium, electroplating experiments from bath with low concentration of trivalent chromium were performed. The variation of current efficiency of chromium electroplating with the electroplating conditions was explained. The maximum current efficiency of pulse plating is 6.4 times as high as that of direct plating at the same mean current density The nodular size increased with pulse plating time and the pulse frequency.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.47-48
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• 2011

The effect of solution acidity and organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was systematically investigated in the view point of solution stability, electroreduction of trivalent chromium ions and characterization of deposition layer. It was found that, the concentration of fraction chromium complexes in the trivalent chromium bath containing formic acid is strongly depended on pH value. PEG molecules were stable in trivalent chromium bath containing formic acid via studies on electrospray ionization mass spectrometry (ESI-MS) and UV-Vis. However, the presence of PEG molecules decreased the reductive current of hydrogen evolution, increasing of current efficiency higher about 10 % compared with solutions without PEG. Moreover, PEG additives developed the nodular morphology during electroreduction of trivalent chromium ions with the increase of solution acidity and enhanced its current efficiency by maintaining the consumption of complexant, formic acid, at a low speed. In this study, the effect of solution acidity was emphasized important, there, it controlled the formation of complexes in the solution, cathodic film (CF) during deposition, and properties of deposited layer. By electrochemical quartz crystal microbalance (EQCM), studies show that chromium electrodeposition occurs via the formation of intermediate complexes and adsorption on the cathode surface, which hinder the penetration of ions from bulk solution to the cathode surface.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.433-442
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• 2006

Hexavalent chromium passivation, as very effective anti-corrosion method, can not be used in the field of surface treatment for metal, any more. Throughout the world, this regulations which was applied to automotive industries will be extended to all industries including electronics industries in the near future. Therefore a new anti-corrosion method should be established without delay, and trivalent chromium passivation as an alternatives replace the hexavalent chromium passivation for the time being. This paper gives an overview of the currently available trivalent chromium passivation processes, and then it attempts to give an insight to develop a more effective trivalent chromium conversion coating process for possible substitution of the hexavalent chromium passivation process.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.6
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• pp.335-340
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• 2003

To improve properties of wear resistance and anti-corrosion of the trivalent chromium platings, oxinitrocarbunsing and steam oxidation were conducted. Armophous trivalent Cr platings could be transformed to chromium carbides of high hardness, that showed low friction and wear rate. Even though micro-cracks were within as platings, superior anti-corrosion property was obtained by these treatments due to healing of cracks at the interface between the trivalent chromium platings and substrate.

• Toxicological Research
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• v.21 no.1
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• pp.15-21
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• 2005

There is now a growing concern about the possible toxicity of heavy metals in cosmetics. Heavy metals can be used as cosmetic ingredients or may be present as low level impurities in some of the raw materials. Chromium derivatives are used as pigments in cosmetics. Chromium is essential and toxic trace elements. Chromium may cause skin allergy. However, the regulations related to cosmetic products give no limit values for Chromium. Hexavalent chromium is significantly more toxic than trivalent chromium. Hexavalent chromium may present a carcinogenic risk at high concentrations. Therefore, it is important to consider oxidation state of chromium when analyze chromium. The purpose of this study is to determine the concentrations of water-soluble trivalent and hexavalent chromium in samples of makeup products, and to assess the safety of cosmetics on the basis of animal sensitization tests using guinea pig. The present study of chromium in 48 makeup products of 12 manufacturers provides a basis for assessing safety of makeup products. Water-soluble hexavalent chromium was not detected in any product. Water-soluble trivalent chromium was detected in only 9 eye shadows out of 48 makeup products, and could not be quantified 3 out of 9 eye shadows. The highest level of water-soluble trivalent chromium was about 10 mg/kg in spite of 90,000 mg/kg of total chromium. The results of animal sensitization tests show that 200 mg/kg of trivalent chromium and 5 mg/kg of hexavalent chromium have no harmful effect. No cross-reaction among these metals was found. Accordingly, the concentrations of water-soluble chromium in makeup products seemed to be safe. The overall results indicate that chromium in cosmetics probably have no significant toxicological effects. However, It is necessary to set guidelines on the maximum permissible concentration of water-soluble chromium in cosmetics.

• Journal of the Korean institute of surface engineering
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• v.37 no.3
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• pp.175-178
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• 2004

The size and number of nano-size defects of thin trivalent chrome layers were determined by small angle neutron scattering (SANS) without breaking the thin chrome layers. Most of defect size of the trivalent chromium prepared in this test conditions is in the range of about 40nm. The number of nano-size defects less than about 40nm of the trivalent chromium layer increases with plating voltage at constant current density From this study, SANS is proved as one of useful techniques to evaluate nano-size defects of thin film layer.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.129-129
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• 2009

Much attention has been recently paid to the trivalent chromium electro-plating for the application of surface finishing, mainly because of the environmental issues. Nevertheless, trivalent chromium plating has several critical issues to be figured out for such applications, including instability of the plating solution, poor property of plates and etc.