CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.
Issue link: http://coatingspromag.epubxp.com/i/72303
ABOVE Tests per formed in close proximity using different test methods as follows: Triangle (ASTM D6677), Circle (ASTM D3359), and Trapezoid (ASTM D4541). ASTM D6677 contains a scale with ratings from 0 to 10. A rating of "10" indicates the coating is extremely difficult to remove with fragments no larger than approximately 1/32" by 1/32" (0.8 by 0.8 mm) removed with great difficulty. A rating of "0" indicates the coating can be easily peeled from the substrate to a length greater than ΒΌ" (6.3 mm). Ratings of 2, 4, 6, and 8 contain simi lar statements. The higher the rating number, the more difficult the coating is to remove and the smaller the paint chips size removed. In accordance with ASTM D6677, any coating removed during the cutting process is to be disre- garded. ASTM D6677 contains several statements about the test method itself and about its relat ionship to other adhesion test methods. These include the following: (1) this method is a quali- tat ive and subject ive test, (2) other adhesion test methods may be useful in obtaining quantitative results, and (3) no known correlation exists between this test method and other adhesion test methods, such as pull-off (ASTM D4541) or adhesion by tape (ASTM D3359). ASTM D6677 contains no preci- sion and bias statement due to this test method's subjective character. Reporting requirements for ASTM D6677 include the following: (1) number of tests, (2) mean and range of the tests, (3) location of the failure (between the first coat and the substrate, between the first and the second coat, or within a coat), (4) structure tested, (5) location and environmental conditions at the time of the test. CLOSING REMARKS ASTM standards and other indus- try standards are consensus standards writ ten with procedures, report ing requirements, and precision and bias statements. The purpose of the proce- dures within a standard is to ensure that different individuals perform the test following the same procedures and that they report the results using the same criteria. However, for some ASTM tests, such as ASTM D6677, no precision and bias statements are included since the test is subjective in nature. When an ASTM test method lists a rating scale, those who perform the test in accordance with the standard must employ the rating scale when reporting the results. Developing an independent rating scale that differs from the scale provided within the standard is not permitted. When a forensic investiga- tor chooses to blatantly disregard the procedures and instructions contained within an ASTM standard and/or devel- ops his or her own rating system, which benef its the cl ient 's predetermined position, he or she is acting irrespon- sibly and not in accord with integrity required for conducting independent, fair investigations. CP July 2012 J www.coatingspromag.com 77