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This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.
This document replaces QC/T 942-2013 Test methods of hexavalent chromium in automotive materials. In addition to structural adjustments and editorial changes, the following main technical changes have been made with respect QC/T 942-2013:
——The application scope of X-ray fluorescence spectrometry is changed (see 4.1 hereof; Clause 1 of Edition 2013);
——The test methods of “qualitative test of hexavalent chromium in metal anticorrosion coating” are changed (see Clause 5 hereof; Clause 4 of Edition 2013);
——The test process and judgment method of "determination of content of hexavalent chromium in metal anticorrosion coating" are changed (see Clause 6 hereof; Clause 5 of Edition 2013);
——The test methods of “determination of content of hexavalent chromium in polymeric materials and electronic materials” are changed (see Clause 7 hereof; Clause 6 of Edition 2013);
——The test methods of “determination of content of hexavalent chromium in leather materials (colorimetric method)” are changed (see Clause 8 hereof; Clause 7 of Edition 2013);
——The “Terms and definitions” is added (see Clause 3 hereof);
——The test methods of “determination of content of hexavalent chromium in leather materials (chromatography)” is added (see Clause 9 hereof);
——The calculation method of fastener surface coating area "three-dimensional surface area measurement method” is added (see A.4 hereof);
——"Annexes E, F and G" are added (see Annexes E, F and G hereof).
This document was proposed by and is under the jurisdiction of SAC/TC 114 National Technical Committee of Auto Standardization.
The previous editions of this document are as follows:
——It was firstly issued as QC/T 942-2013 in 2013;
——This edition is the first revision.
Test methods of hexavalent chromium in automotive materials
1 Scope
This document specifies the terms and definitions for detection of hexavalent chromium in automotive materials, X-ray fluorescence spectrometry, qualitative test of hexavalent chromium in metal anticorrosion coating, determination of content of hexavalent chromium in metal anticorrosion coating, determination of content of hexavalent chromium in polymeric materials and electronic materials, determination of content of hexavalent chromium in leather materials (colorimetric method), determination of content of hexavalent chromium in leather materials (chromatography) and test report, etc.
This document is applicable to the qualitative and quantitative tests of hexavalent chromium in automotive materials.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
GB/T 30512 Requirements for prohibited substances on automobiles
QB/T 2262 Terminology of leather industry
QB/T 2706 Leather - Chemical, physical, mechanical and fastness tests - Sampling location
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 30512 and QB/T 2262 and the following apply.
3.1
homogeneous material
material with the components or assemblies not able to be further separated by mechanical means (such as unscrewing, cutting, rolling, scraping, and grinding) and constitution of all parts being the same
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3.2
equivalent comparison standard solution
standard solution that can be equivalently replaced according to the standard requirements without affecting the detection and analysis results
3.3
part
components in the initial state that have not been processed according to the sample preparation step therefore cannot be tested
3.4
sample
components that have been processed according to the sample preparation step therefore can be tested or parts capable of being directly tested without sample preparation
4 X-ray fluorescence spectrometry
4.1 Principle
After the part is prepared into a sample, the sample is placed in the sample room of the X-ray fluorescence spectrometer, and the content of hexavalent chromium in the sample (counted by total chromium) is analyzed by X-ray fluorescence spectroscopy according to the selected analysis mode, and whether the content of hexavalent chromium in the sample (counted by total chromium) is qualified and whether hexavalent chromium quantitative detection is needed is judged according to the screening limit value.
This method is suitable for screening and quickly determining the content of hexavalent chromium (counted by total chromium) in automobile materials by X-ray fluorescence spectrometer, but not for determining the content of hexavalent chromium (counted by total chromium) in metal anticorrosion coating.
4.2 Reagents and materials
4.2.1 Unless otherwise stated, only the recognized analytical reagents and distilled water or deionized water or water with equivalent purity shall be used during the analysis.
4.2.2 Boric acid: Guaranteed reagent, baked at 105℃ for 1 h, stored in a dryer.
4.2.3 Anhydrous lithium tetraborate: Guaranteed reagent, burned at 700℃ for 4 h, stored in a dryer.
4.2.4 Liquid nitrogen: Industrial grade.
4.2.5 Reference materials containing chromium.
4.2.6 Polyester film.
4.3 Apparatus
4.3.1 X-ray fluorescence spectrometer.
4.3.2 Cutting machine.
4.3.3 Liquid nitrogen cryogenic pulverizer.
4.3.4 Grinder: Grinding tool with wolfram carbide (WC).
4.3.5 Tablet machine: With the working pressure not less than 20 MPa.
4.3.6 Sample melting machine: With the working temperature not lower than 1,150℃.
4.4 Sample
4.4.1 Sample preparation principle
4.4.1.1 The sample used for analysis must cover the measurement window of the spectrometer.
4.4.1.2 The illuminated surface of the sample shall be able to represent the whole sample.
4.4.1.3 The sample shall be protected against contamination during preparation.
4.4.2 Sample preparation method
4.4.2.1 Solid part
Parts shall be analyzed directly if they are made of homogeneous material with flat surface and a size meeting the requirements of X-ray fluorescence spectrometer. Small parts with flat surface may be put together for analysis. Thin parts may be stacked together to a sufficient thickness (at least 5 mm thick and maintaining thickness consistency and composition uniformity) for analysis. In order to spread out the sample smoothly, lining material may be added as support, and lining material with low background shall be selected as far as possible.
Foreword iv
1 Scope
2 Normative references
3 Terms and definitions
4 X-ray fluorescence spectrometry
5 Qualitative test of hexavalent chromium in metal anticorrosion coating
6 Determination of content of hexavalent chromium in metal anticorrosion coating
7 Determination of content of hexavalent chromium in polymeric materials and electronic materials
8 Determination of content of hexavalent chromium in leather materials (colorimetric method)
9 Determination of content of hexavalent chromium in leather materials (chromatography)
10 Test report
Annex A (Informative) Method for calculating coating surface area of fasteners
Annex B (Normative) Determination of content of hexavalent chromium in polymeric materials and electronic materials - Determination of recovery rate and limit of detection
Annex C (Normative) Determination of content of volatile matters in leather materials
Annex D (Normative) Determination of content of hexavalent chromium in leather materials - Determination of recovery rate (colorimetric method)
Annex E (Informative) Chromatographic conditions for direct detection method
Annex F (Informative) Chromatographic conditions for post-column reaction method
Annex G (Normative) Method for determination of content of hexavalent chromium in leather materials - Determination of recovery rate (chromatography)
