Journal of the Korean Industrial and Engineering Chemistry, Vol.14, No.7, 959-967, November, 2003
유기 착화제의 형태에 따른 3가 크롬 전착 특성
Electrodeposition Characteristics of Trivalent Chromium According to Types of Organic Complexing Agent
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초록
효율성 있는 3가 크롬 전착공정 개발을 위하여 기본 전착욕을 크롬 원재료로서 Cr2(SO4)3, 전도도 개선제로 K2SO4, Na2SO4, KCl, pH 완충제로 H3BO3, 계면활성제로서 Triton-X로 구성하고, 이 전착욕에서 ammonium formate, sodium formate, glycine, 및 formic acid의 4가지 종류의 유기착화제가 3가 크롬 전착공정에 미치는 영향을 조사하였다. 전착공정은 양이온 교환막을 사용하여 양극실과 음극실을 분리한 double cell에서 진행하였다. 양극과 음극은 Pb-5% Sn 판과 구리판이 각각 사용되었으며 anolyte는 10% H2SO4 용액이 사용되었다. 조사된 4가지 유기착화제중 formic acid가 가장 우수한 효능을 나타내었다. 35 ml/L의 formic acid 농도, 22 A/dm2 ~ 26 A/dm2 범위의 전류밀도 조건에서 가장 높은 전류효율 36%를 나타내었으며, 11.41 μm 두께의 전착피막이 얻어졌다. 이 전착피막의 SEM 분석 결과 전형적인 크롬 전착피막의 특징인 microcrack이 관찰되었다.
The effects of organic complexing agents such as, ammonium formate, sodium formate, glycine and formic acid on the electrodeposition was investigated to find an optimum process for the trivalent chromium plating. The basic bath was consisted of Cr2(SO4)3 as the chromium source, K2SO4, Na2SO4, and KCl as improving agent of conductivity, H3BO3 as the buffering agent, and Triton-X as the wetting agent. Electrodeposition was carried out in a double-cell by using a cation exchange membrane separating the anode and cathode compartments. The anode and cathode were composed of Pb-5% Sn plate and a copper plate, respectively and the anolyte was a 10% H2SO4 solution. Among the four investigated organic complexing agents, the formic acid proved to be most effective. The high current efficiency of 36% was obtained under the condition of formic acid concentration of 35 mL/L and current density in the range from 22 to 26 A/dm2. The chromium plate with the thickness of 11.41 μm was obtained. The SEM observation of the chromium plate surface electrodeposited revealed a microcrak which is a typical characteristic of chromium plate.
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