Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Development of the Cr6+ and Cr3+ Continuous Analyzer for the Process Control of the Chromate Treating Solution
Yasuo INOKUMATakashi OCHIAIJyo ENDOMinoru NISHIHARA
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1980 Volume 66 Issue 2 Pages 263-270

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Abstract

The concentration of Cr6+ and Cr3+ in the chromate treating solution must be maintained exactly at the constant levels for getting the good coating.
We studied in detail about the absorption curves of Cr6+ and Cr3+to develop the most suitable analyzer of Cr6+ and Cr3+ for the process control in the chromate treating plants. It was found out at the result of this study that the best method was to measure the absorbance at around 545nm and 620nm with the two wavelength spectrophotometer to determine Cr6+ and Cr3+. This colorimeter could be manufactured easily by the simple combination of the I.C. units.
020 000ppm of Cr6+ and 02 000 ppm of Cr3+ in the chromate treating solution could be determined continuously by using this analyzer with the standard deviation (σd) of 105ppm (Cr6+) and 15 ppm (Cr3+) to the values of the chemical analyses. The stability of this analyzer in the running test of 12 hours was 110ppm (Cr6+ : 5 500ppm) and 17ppm (Cr3+ : 750ppm) in R (the difference between max. and min.).
This analyzer was freed from the interference with Fe3+, Zn2+, So2-4, No3-, CH3COO-, suspended sludge, and bubble in the case of Cr6+ and Fe3+, Zn2+, So2-4, No3-, and CH3COO- in the case of Cr3+.

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© The Iron and Steel Institute of Japan
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