• 한국표면공학회지
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• 제16권4호
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• pp.188-194
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• 1983

The method of trivalent chromium plating has been studied. The relations between the mixing ratio of chromic chloride and DMF, and the corrosion resistance and throwing power of plated chromium have been investigated. As a result, the best result has been obtained, when the mole ratio of chromic chloride and DMF are 0.8 and 5.4M respectively, and it has been learned that the amounts of DMF added have particularly the delicate effects in chromium plating procedures. The results of measuring of pH and reduction potentials of chromium plating bath with addition of DMF showed that the functions of DMF have both the buffer actions for the solution and the complex formation of trivalent chromium.

• 한국표면공학회지
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• 제37권2호
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• pp.86-91
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• 2004

Effect of potassium formate, glycine and oxalic acid in a sulfate solution on the deposit composition and current efficiency of trivalent chromium plating was studied. The trivalent chromium layers prepared by solutions with potassium formate, glycine and oxalic acid contain a few carbon inside. The solutions containing potassium formate, glycine and oxalic acid are relatively stable with pH change. The solution with the potassium formate shows 6-30％ current efficiency with current density, whereas, the solutions with oxalic acid and glycine show about 5％ current efficiency, respectively. The improved current efficiency is related to enough supply of chromium ions to the electrode due to the increase of pH at the front of electrode.

• 한국표면공학회지
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• 제36권2호
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• pp.155-160
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• 2003

The effect of the temperature, current density and deposit time on hard chromium deposition in trivalent chromium bath was investigated. Cathode current efficiency increased with increasing current density. Increasing bath temperature from $20^{\circ}C$ to $50^{\circ}C$, chromium deposits were produced in higher current density and the maximum current efficiency was increased. At the plating conditions of $40^{\circ}C$, $30A/dm\m^2$, the deposition thickness increased in proportion to increasing electrolysis time The rate is$ 90\mu\textrm{m}$/hrs. for 2 hours. Microhardness of chromium deposits increased with increasing bath temperature and decreasing current density, and it was constant with electrolysis time. All of bath conditions, microstructure of chromium deposits has nodular structure with some cracking pattern and nodule size increased with increasing deposit thickness.

• 한국표면공학회지
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• 제43권6호
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• pp.297-303
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• 2010

The effect of solution acidity and organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was systematically investigated in the view point of electroreduction of trivalent chromium ions and solution stability. It was found that solution acidity controlled at pH 2.5 showed the widest current range for bright electrodeposits in the presence of PEG additives, which reduced the local current intensification at high current densities. Through complex interaction between PEG additives and hydrogen ion, that is, solution acidity, electrode potential was moved in the negative direction in the bulk solution, while it shifted in the positive when electric potential was scanned. In conjunction with electrochemical quartz crystal microbalance (EQCM), it was found that PEG additives had a role in promoting the electron transfer to trivalent chromium ion complexes in bulk solution and their adsorption at the electrode surface as well as interfering with hydrogen ion reduction process below pH 2.5. The 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 low speed.

• Journal of Ceramic Processing Research
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• 제19권6호
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• pp.455-460
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• 2018

Chromium plating is a common surface treatment technique extensively applied in industry due its excellent properties which include substantial hardness, abrasion resistance, corrosion resistance, surface color, and luster. In this study, the effect of PTFE on corrosion behavior of Cr-P plating, low carbon steel substrates are electroplated in Cr(III) baths without and with PTFE. Trivalent chromium carbon plating was electroplated from trivalent chromium sulfate-based baths with different PTFE dispersion contents. The study focused on the microstructure, PTFE content, roughness, and corrosion resistance of the Cr-P-PTFE composite plating. Scanning electron microscopy and atomic force microscopy images showed a smoother plating and a decrease in the surface roughness of the electrodeposited. The results demonstrate that PTFE eliminates the cracks within plating by reducing internal stress. Therefore, the corrosion resistance of Cr-P-PTFE composite platings were better than that of Cr-P alloy platings.

• Applied Microscopy
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• 제17권1호
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• pp.29-46
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• 1987

To study hexavalent chromium effects on mitochondrial electron transport, the activities of electron transport enzymes and conformational change of mitochondria treated with $40{\mu}M$ of sodium dichromate ($Na_{2}Cr_{2}O_{7}\;2H_{2}O$) were investigated. And so were those of liver mitochondria isolated from mouse intraperitoneally injected with sodium dichromate, 40mg per kg body weight. On both treatment with chromium(VI), the activities of electron transfer enzymes (Complex I and IV) were increased to some extent and the ultrastructural transformation of mitochondria from a condensed to an orthodox conformation was inhibited under State IV respiration. These results represent' inhibitory effect of hexavalent chromium on electron transport without inhibiting electron transfer enzymes (Complex I and IV) in mitochondria. On intraperitoneal treatment with hexavalent chromium as sodium dichromate and trivalent chromium as chromic chloride, containing 37.5 mg of chromium per kg body weight, respectively, the activities of electron transfer enzymes of liver isolated from mouse with chromium(VI) was reduced, but that with chromium(III) was not affected. And with chromium(VI), all mice after 12 hours of treatment died, only after 6 hours survived. With chromium(III), however, all survived. This indicates that hexavalent chromium is more toxic than trivalent chromiumin mouse liver.

• 한국식품영양과학회지
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• 제33권4호
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• pp.762-768
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• 2004

인슐린 작용을 강화시키는 LMWCr의 발견과 크롬 결핍과 관련 있는 포도당 불내성(glucose intolerance)이 크롬 투여 시 반응을 보여준 임상적 증명 이후, 크롬은 확실한 필수 영양소로 인식되고 보조제로 사용되고 있다. 시험관 실험에서 고농도의 3가 크롬을 배양 세포에 노출 시, 일부 연구 결과에서 염색체이상 유발과 변이원성 효과가 발견되긴 하였으나 이는 비타민 A, D, 니코틴산, 셀레늄 등과 같은 많은 다른 영양소의 과잉 섭취 시 독성 효과를 나타내는 정도로 해석되며, 시험관 실험 결과들이 발암성의 증거로 해석되지는 않는다. 3가 크롬을 경구 보조제로 투여된 임상 치료에서 환자들은 독성효과를 보이지 않았으며, 혈장 내 크롬 수치가 비 투여된 사람들에 비하여 조금 높았다. 크롬을 TPN 형태로 투여받은 환자들에게서도 우려했던 신체ㆍ정신적 효과와의 상관 관계가 없었으며 신기능부전을 나타낸 경우는 신장 독성을 주는 약들을 함께 복용한 경우로서, 우려되는 부작용은 없는 것으로 인정된다. 임상학적, 실험적으로 사용된 3가 크롬의 용량은 ESADDI 규정된 범위 50∼200 $\mu$g/day에서 전혀 독성을 나타내지 않았으며, 일반적인 사용에 기준이 될 것이다. EPA는 모든 관련 자료들을 검토한 후에 크롬의 참고용량 (RfD) 수치를 70 mg/day로 결론지었으며, 다른 영양소들의 용량과 비교했을 때 대단히 넓은 수치이다. 3가 크롬은 당뇨병, 임신성 당뇨병, 인슐린 내성, 비정상적 지방대사를 개선시키기 위한 영양소로서 가능성을 가진다. 또한 크롬의 보충은 제II형 당뇨병과 다양한 심혈관계 질환을 예방하거나 치료하는데 가장 유용한 것으로 밝혀졌다. 앞으로는 크롬 보조제 사용 시, 일부 연구자들이 3가 크롬 1000 $\mu$g/day의 안전성을 입증한 것과 같이 용량을 늘려 임상실험을 시도한 후 안전과 효능을 증명하는 것이 필요하다.

• 한국산업보건학회지
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• 제34권2호
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• pp.166-178
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• 2024

Objectives: The 12 occupational exposure limits(OELs) for chromium and its compounds in Korea were set by applying the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs). However, this is significantly different from the TLVs after the existing TLVs were integrated and withdrawn in 2018, so it is necessary to review the revision. Methods: Various documents related to chromium OELs were reviewed, including the ACGIH TLV Documentations for chromium and its compounds. A field survey was conducted targeting workplaces handling chromium and its compounds. Based on this, a revised OELs were proposed and a socio-economic evaluation was conducted. Results: The OELs for chromium compounds in Korea was first enacted in 2002, and in 2007, the OELs for chromium (hexavalent) compounds (insoluble) was lowered from 0.05 mg/m³ to 0.01 mg/m³. In 2008, the OELs for strontium chromate was newly established as 0.0005 mg/m³, and in 2018, the OELs for calcium chromate was newly established as 0.001 mg/m³. Total chromium and hexavalent chromium were measured for each of 6 samples at 2 welding sites, 4 plating sites, and 2 spray coating sites. When omparing the average of the results measured by ICP, a total chromium analysis method, and the analysis results by IC, a hexavalent chromium analysis method, only workplace 4 was the same, and total chromium was evaluated more, and total chromium was evaluated at 0.0004 to 0.0027 mg/m³. And hexavalent chromium was evaluated as non-detection ~ 0.0014 mg/m³. Amendment ①: The exposure standard for hexavalent chromium is not divided into water soluble, insoluble, chromium ore processing, and other hexavalent chromium compounds, and is integrated into 0.01 mg/m³, which is the level of chromium (hexavalent) compound (insoluble)., OELs for chromium (metal) and chromium (trivalent) compounds are integrated into chromium (trivalent) compounds, and the exposure level is maintained. Amendment ②: As in the amendment ①, the OELs are integrated, but the level is lowered to 0.005 mg/m³, which is the OELs of OSHA, and there is a grace period of 4 years. Amendment ③: As in the amendment ①, the OELs are integrated, but the level is lowered to 0.0002 mg/m³, which is the exposure standard of ACGIH, and there is a grace period of 5 years. Conclusions: Amendment ①: The change in the OELs is insignificant, so the cost required is small, and the benefit/cost ratio is greater than 1, so there is no problem in applying the amendment. Amendment ②: In all scenarios except chromium 6(insoluble), the benefit/cost ratio is greater than 1, so it is thought that there will be no major problem in applying the amendment. Amendment ③: Since the benefit/cost ratio is less than 1 in all scenarios, it is thought that the total social benefit that can be obtained when applying the amendment is not large.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2003년도 춘계학술발표회 초록집
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• pp.25-25
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• 2003

• 한국표면공학회지
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• 제37권1호
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• pp.13-21
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• 2004

The deposition rate, the current efficiency and surface morphology of trivalent Cr deposits were investigated according to additives in sulfate bath and current density. The deposition rate of the Cr deposits plated from the formic acid complexed bath was noticeably higher than that of the glycine complexed bath. The current efficiency of the deposition from formic acid bath was higher than that of the glycine bath and increased with current density in the range of 20-50 A/d$\m^2$. The current efficiency of the deposition from the formic acid bath with boric acid buffer was higher than that of the bath with aluminum sulfate or boric acid-aluminum sulfate buffers. The nodular crystallite size of the Cr deposits increased with current density and the uniform and crack-free growth of the deposits for the aluminum sulfate was observed compared to the other buffers.