J. Technology and Education, Vol.18, No.1, pp.21-27, 2011
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i*, MM
HƍwZ Hw(193-0997qsc1220-2)
* shoji@tokyo-ct.ac.jp
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Metal leaching toxicity and stability of persimmon tannin plate film
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Ryo Shoji and Takanobu Sato
Department of Chemical Science and Engineering,
Tokyo National College of Technology, Hachioji, Tokyo 193-0997, Japan
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(Received February 24, 2011; Accepted March 31, 2011)
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Abstract
The toxicity of hexavalent chromium was the focus of the EU RoHS (Restriction of Hazardous Substances) directive. Hexavalent chromium has been used as plating material. Therefore, there is some urgency to the development of an alternative material for conversion coating. Persimmon tannin is an oxblood liquid made from astringent persimmon, which is anticorrosive and antiseptic. Persimmon tannin is one of several environmentally acceptable alternatives with equivalent or better performance properties. Persimmon tannin plate films consist of organic matter. A metal plate coated with persimmon tannin was used as the test material. Firstly, the corrosion products by resistance to neutral spray test[1] of persimmon tannin plate was characterized by an X-ray diffraction (D8ADVANCE; Bruker axs), infrared. First, the corrosion products by resistance to the neutral spray test [1] of a persimmon tannin plate were characterized using an X-ray diffraction (D8ADVANCE; Bruker Axs), and an infrared spectrometer (FT-IR620; JASCO CORPORATION). The XRD patterns of the corrosion products revealed the state of zinc hydroxychlorides (Zn5(OH)8Cl2H2O). Secondly, the top surface of the coating was examined by scanning with an FE-SEM (QUANTA FEG250: FEI). Leaching tests were performed on the persimmon tannin plate. The concentration of zinc in aqueous samples was analyzed using inductively coupled plasma - atomic emission spectrometry (SPS7800; SII). The toxicity of the leachate and plating materials was determined with a Rapid Onsite Toxicity Audit System (ROTASR) assay. These results indicated that the performance of the persimmon tannin plate was better than that of the chromate plate.
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Keywords: persimmon tannin plate, leaching toxicity, zinc hydroxychloride, hexavalent chromium, gallic acid, tannic acid
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