5.1 In order for a coating is to fulfill its function of protecting or decorating a substrate, the coating must remain adhered to the substrate. Because the substrate and its surface preparation (or lack thereof) have a drastic effect on the adhesion of coatings, a method to evaluate adhesion of a coating to different substrates or surface treatments, or of different coatings to the same substrate, is of considerable usefulness in the industry.

5.2 This test method is limited to evaluating lower levels of adhesion (see 1.3). The intra- and inter-laboratory precision of this test method is similar to other test methods for coated substrates (for example, Test Method D2370 and Test Method D4060), and is insensitive to all but large differences in adhesion. Limiting the range of rankings from 0 to 5 reflects the inability of this test method to make fine distinctions between levels of adhesion. Users shall not use intermediate values for ranking adhesion tests within this method.

5.3 Extremes in temperatures or relative humidity may affect the adhesion of the tape or the coating.

5.4 A given tape may not adhere equally well to different coatings due to several factors, including differences in coating composition and topology. As such, no single tape is likely to be suitable for testing all coatings. Furthermore, these test methods do not give an absolute value for the force required for bond rupture, but serves only as an indicator that some minimum value for bond strength was met or exceeded (1, 2).6

5.5 Operators performing these test methods must be trained and practiced in order to obtain consistent results. The accuracy and precision of the test result obtained by using these methods depends largely upon the skill of the operator and the operator's ability to perform the test in a consistent manner. Key steps that directly reflect the importance of operator skill include the angle and rate of tape removal and the visual assessment of the tested sample. It is not unexpected that different operators might obtain different results (1, 2).

5.6 The standard requires that the free end of the tape be removed rapidly at as close to a 180° angle as possible. When the peel angle and rate vary, the force required to remove the tape can change dramatically due to the rheological properties of the backing and adhesive. Variation in pull rate and peel angle can effect large differences in test values and must be minimized to assure reproducibility (3).

Note 1: These test methods have been reported being used to measure adhesion of organic coatings on non-metallic substrates (for example, wood and plastic), although related precision and bias data is lacking. If testing coatings on non-metallic substrates, either Test Method A or Test Method B may be more appropriate and the method employed should be discussed by interested parties. Issues with plastic substrates are noted in Appendix X1. A similar test method, ISO 2409, permits tests on non-metallic substrates (for example, wood and plaster). Precision and bias data on the latter is lacking. Test Method D3359 was developed with metal as the substrate and, in the absence of supporting precision and bias data, is so limited.

1.1 These test methods cover procedures for assessing the adhesion of relatively ductile coating films to metallic substrates by applying and removing pressure-sensitive tape over cuts made in the film.

1.2 Test Method A is primarily intended to rate the adhesion of coatings and coating systems greater than 125 μm (5 mils) in total thickness, while Test Method B is primarily intended to rate the adhesion of coatings and coating systems less than 125 μm (5 mils) in total thickness. Test Method B is not considered suitable for films thicker than 125 μm (5 mils) unless wider spaced cuts are employed and there is an explicit agreement between the purchaser and seller. If the thickness of the coating or coating system has not been predetermined, employ the use of a standard such as Practice D7091 or other appropriate standard agreed upon by interested parties prior to proceeding.

1.3 These test methods are used to evaluate whether the adhesion of a coating to a substrate is adequate for the user’s application. They do not distinguish between higher levels of adhesion for which more sophisticated methods of measurement are required.

1.4 This test method is similar in content (but not technically equivalent) to ISO 2409.

1.5 In multicoat systems adhesion failure may occur between coats so that the adhesion of the coating system to the substrate is not determined.

1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.