1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW3034 Absence of Hexavalent Chrome, Cr VI, in Coatings Copyright 2012 General Motors Company All Rights Reserved September 2012 Originating Department: GME Specification Center Page 1 of 3 1 Scope Note: Nothing in this standard supercedes applicable
2、laws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. This test is used to prove the absence of Cr VI in coatings. 1.2 Foreword. This test method is derived from ISO 3613 Test Fluid C and is equivalent
3、 to EN 15205. 1.3 Applicability. Not applicable. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. EN 15205 ISO 3613 2.2 GM Standards/Specifications. None 3 Resources 3.1 Facilities. Not applicable. 3.2 Equipment.
4、3.2.1 Ordinary Laboratory Apparatus. 3.2.2 Colorimeter or Spectrophotometer. With a colorimeter, use a filter having a mean transmission of 540 nm. A wavelength of 540 nm shall be set for the spectrophotometric measurement. Use an absorption cell with an optical path length of 1 cm in both cases. 3.
5、3 Test Vehicle/Test Piece. 3.3.1 Coating materials. 3.3.2 Reagents. Use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. 3.3.2.1 Sulfuric Acid, 4.5 M. Mix three (3) volumes of water with one (1) volume of concentrated sulfuric acid (1.84 g/ml). No
6、te: When preparing sulfuric acid solution wear safety glasses. Take a vessel of heat resistant glass and fill it with three (3) volumes of water. Add one (1) volume of concentrated sulfuric acid slowly or in small portions, while stirring the water. Never pour water into concentrated sulfuric acid.
7、3.3.2.2 Diphenylcarbazide Solution. Dissolve 0.5 g of diphenylcarbazide in 50 ml of acetone. Dilute slowly, while stirring, with 50 ml of water (rapid mixing may result in precipitation of diphenylcarbazide). For maximum stability store under refrigeration in an amber colored glass bottle. Note: Be
8、aware that diphenylcarbazide is a cancer producing material. When handling it, make sure that you do not breathe in the dust or get otherwise in contact with it. 3.3.2.3 Cr VI Standard Solution. Dissolve 0.113 g K2Cr2O7 in water and dilute it in a volumetric flask to 100 ml. Pipette 0.25 ml of this
9、solution into a second 100 ml volumetric flask and dilute to the mark with water. The second solution contains 1 Pg Cr VI per ml (5 ml = 5 Pg Cr VI). 3.4 Test Time. Not applicable. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction
10、 or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3034 Copyright 2012 General Motors Company All Rights Reserved September 2012 Page 2 of 3 3.5 Test Required Information. Not applicable. 3.6 Personnel/Skills. Not applicable. 4 Procedure 4.1 Preparation. The
11、test sample shall have a surface area of (50 r 5) cm. From small parts take the suitable number of samples. From larger parts, use only a (50 r 5) cm segment. 4.2 Conditions. 4.2.1 Environmental Conditions. See paragraph 4.3. 4.2.2 Test Conditions. Deviations from the requirements of this standard s
12、hall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. 4.3 Instructions. The test sample is leached with boiling water for 5 minutes. Hexavalent chrome compounds will react with diphenylcarbazide and form a red colored complex that ca
13、n be observed visually, and, or detected colorimetrically or spectrophotometrically. 4.3.1 Place the sample in a 100 ml beaker with volume graduation, or other suitable beaker with volume graduation. Add 50 ml water. Heat the water to boiling and keep it boiling for exactly 5 minutes. 4.3.2 Remove t
14、he test piece and cool the beaker and its contents to (+23 5) C. Fill up with water to 50 ml if some water evaporated. If the solution is milky or has a precipitate, filter through a paper filter into a dry beaker. Add 1.5 ml of dilute sulfuric acid solution (4.5 M) and 1 ml of diphenylcarbazide sol
15、ution; then mix well. Evaluate the color against the comparison solution (see “Comparison Solution Preparation”). A red color indicates Cr VI. 4.3.3 If a clear evaluation against the comparison solution is not possible visually, the sample is poured into an absorption cell and after a reaction time
16、of 2 minutes, it is measured with a spectrophotometer against the comparison solution. 4.3.4 Colorimetric or spectrophotometric measurement shall be performed when water leaching produces a colored solution which interferes with the visual evaluation. 4.3.5 Comparison Solution Preparation. 4.3.5.1 F
17、or comparison, dilute 5 ml of the Cr VI-standard solution (5 ml = 5 Pg Cr VI) to 50 ml with water. This solution is treated in the same way as the sample solution (see paragraph 4.3). 4.3.5.2 If according to this method, the coating is found to be Cr VI free, it still may be that a Cr VI containing
18、prime coat is covered by a Cr VI free top coat. In this case, scrape the coating in thin layers with a suitable instrument and test against the test sample together with the coating particles. 5 Data 5.1 Calculations. Not applicable. 5.2 Interpretation of Results. The coating is accepted to be free
19、of Cr VI (0.1 g/cm2) if the red color of the test sample solution is less than the comparative solution visually, or the absorption of the sample solution at 540 nm is less than the comparative solution absorption at 540 nm. 5.3 Test Documentation. With reference to this Test Procedure, the test res
20、ults shall be presented in a test report. 6 Safety This standard may involve hazardous materials, operations, and equipment. This standard does not propose to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safet
21、y and health practices and determine the applicability of regulatory limitations prior to use. 7 Notes 7.1 Glossary. Not applicable. 7.2 Acronyms, Abbreviations, and Symbols. Not applicable. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo re
22、production or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3034 Copyright 2012 General Motors Company All Rights Reserved September 2012 Page 3 of 3 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: Test to GM
23、W3034 9 Release and Revisions This standard was originated in March 1998. It was first approved by Finishes and Coatings GSSLT in October 1999. It was first published in October 1999. Issue Publication Date Description (Organization) 1 OCT 1999 Initial publication. 2 APR 2001 Editorial, Section 4.2.
24、3 (GM) 3 SEP 2006 Added information on DIN standard and adapted legal limit in section 6 (GM) 4 SEP 2012 5year refresh / transfer to new template (GM) Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
