1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW14865 Determination of Scratch Resistance of Organic Coatings - Simulation of Car Wash Installations Copyright 2012 General Motors Company All Rights Reserved June 2012 Originating Department: North American Engineering Standards Page 1 of 6 1 Scope
2、 The purpose of this test is the simulation of a car washing installation and the determination of the scratch resistance of organic coatings. Note: Nothing in this standard supercedes applicable laws and regulations. Note: In the event of conflict between the English and domestic language, the Engl
3、ish language shall take precedence. 1.1 Purpose. Not applicable. 1.2 Foreword. Not applicable. 1.3 Applicability. Not applicable. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ASTM D2486 DIN 67530 ISO 2813 DIN
4、12605 ISO 787-7 2.2 GM Standards/Specifications. GMW3221 2.3 Additional References. None 3 Resources 3.1 Facilities. Not applicable. 3.2 Equipment. 3.2.1 Test Equipment. 3.2.1.1 Test devices for sample pre-treatment according to GMW3221 Code B. 3.2.1.2 Gloss measuring instrument (e.g., micro-TRI-glo
5、ss, Byk-Gardner). 3.2.1.3 Washability and abrasion tester with brush and brush holder according to ASTM D2486 (e.g., Model 494, Erichsen). 3.2.1.4 Suitable precision balance. 3.2.1.5 Drying oven capable of maintaining the specified temperatures according to this test procedure. 3.2.1.6 Micronized Ca
6、lcium Carbonate with the following characteristics: Chemical composition: CaCO3 98.5% MgCO3 0.8% Fe2O3 0.1% Hardness: 3 Mohs Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM
7、 WORLDWIDE ENGINEERING STANDARDS GMW14865 Copyright 2012 General Motors Company All Rights Reserved June 2012 Page 2 of 6 Density: 2.7 g/cm3 Particle size distribution: Sieve residue 45 m (ISO 787-7): 0.1% Upper cut (D 98%): 12 m Average particle diameter (D 50%): 2.5 m Particle proportion 70) shall
8、 be measured with 20 meter geometry. Low gloss finishes (10 to 70) shall be measured with meter geometry. 5 Data 5.1 Calculations. Not applicable. 5.2 Interpretation of Results. Not applicable. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo
9、 reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14865 Copyright 2012 General Motors Company All Rights Reserved June 2012 Page 4 of 6 5.3 Test Documentation. 5.3.1 Evaluation and Rating. Abrasion tester and brush holder shall be calibrated acc
10、ording to ASTM D2486. The brush conditions shall be checked in regular periods and exchanged if necessary, for example, when the protruding bristles have a length 19 mm in soaked condition (or 18 mm in dry condition) or the bristles are damaged or deformed. Furthermore, the brush shall be exchanged
11、after a maximum of 100 000 double strokes or an application period of three (3) years. 5.3.1.1 The gloss is measured immediately after stressing. In each case, the gloss measuring instrument shall be positioned parallel to the scratches for test cycle I (25 double strokes) and test cycle II (200 dou
12、ble strokes) on the previously, precisely defined measurement points (see Figure 1) and the gloss (20 or 60 optic) shall be measured according to DIN 67530/ISO 2813. Both gloss values G25 and G200 shall be determined via calculation of the mean value. 5.3.1.2 The test samples shall then be stored fo
13、r 1 hour in a heating cabinet at a temperature of (+80 3) C and shall be measured analogously to paragraph 5.3.1.1 after heat treatment. The gloss values G25(recovery) and G200(recovery) are obtained. 5.3.1.3 The result of the scratch test shall be specified in percent (%) gloss reduction after 25 o
14、r 200 double strokes. Gloss reduction (L) is calculated using the following formula: L25 = 100% L200 = 100% The values L25 and L200 characterize the scratch resistance of paint surfaces immediately after stressing. However, as organic coatings are able, to some extent, to recover from this stressing
15、 it is important to determine the values L25(recovery) and L200(recovery), which better describe the characteristics of paint surfaces in respect of their behavior in car washing installations. L25(recovery) = 100% L200(recovery) = 100% The calculated values L25(recovery) and L200(recovery) serve t
16、o characterize scratch resistance. 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 safety and h
17、ealth practices and determine the applicability of regulatory limitations prior to use. 7 Notes 7.1 Glossary. Not applicable. 7.2 Acronyms, Abbreviations, and Symbols. L Gloss reduction Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reprodu
18、ction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14865 Copyright 2012 General Motors Company All Rights Reserved June 2012 Page 5 of 6 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: Test to GMW14865 9
19、Release and Revisions This standard was originated in November 2005. It was first approved by the Global Materials Team in September 2006. It was first published in January 2007. Issue Publication Date Description (Organization) 1 JAN 2007 Initial publication. 2 JUN 2012 Updated references, content
20、change. (Finishes & Coatings GSSLT) Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW14865 Copyright 2012 General Motors Company All Right
21、s Reserved June 2012 Page 6 of 6 Appendix A The abrasive medium Calcium Carbonate with the trade name “Millicarb BG” is a commonly used extender in the paint-rubber-plastic and related industries. It was selected because it can be mixed to a smooth slurry without using a wetting agent and produces i
22、n test very similar scratches to those produced in car wash installations. Similar products from other sources may be used but shall be compared initially in test to Millicarb BG. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
