Astm D6677

Standard Test Method for
Evaluating Adhesion by Knife1

This standard is issued under the fixed designation D 6677; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the lastrevision or reapproval.


1. Scope
1.1 This test method covers the procedure for assessing the adhesion of coating films to substrate by using a knife.
1.2 This test method is used to establish whether the adhesion of a coating to a substrate or to another coating (in multi-coat systems) is at a generally adequate level.

NOTE 1—The term “substrate” relates to the basic surfaceon which a coating adheres (may be steel, concrete, etc. or other coating).
1.3 This method can be used in the laboratory and field.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility ofthe user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use.

2. Referenced Documents
2.1 ASTM Standards:
D 2197 Test Methods for Adhesion of Organic Coatings by
Scrape Adhesion.2
D 3359 Test Methods for Measuring Adhesion by Tape
Test.2
D 4541 Test Method for Pull-Off Strength ofCoatings
Using Portable Adhesion Testers.3

3. Summary of Test Method
3.1 Adhesion is determined by making an “X” cut into the coating film to the substrate and by lifting the coating with a knife. Adhesion is evaluated qualitatively on a 0 to 10 scale.

4. Significance and Use
4.1 Coatings, to perform satisfactorily, must adhere to the substrates on which they are applied. This test method hasbeen found useful as a simple means of assessing the adhesion of coatings. Although this method is a qualitative and a subjective test it has been used in industry for many years and can provide valuable information.


1 This test method is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, and Applications and is the direct responsibility of Subcom- mittee D01.46 onIndustrial Protective Coatings.
Current edition approved May 10, 2001. Published July 2001.
2 Annual Book of ASTM Standards, Vol 06.01.
3 Annual Book of ASTM Standards, Vol 06.02.

4.2 Other adhesion test methods may be useful in obtaining quantitative results. See D 2197, D 3359 and D 4541.
4.3 The Performance Evaluation Scale (see 7.4, Table 1) is based on both the degree of difficulty toremove the coating from the substrate and the size of removed coating.
4.4 This test method does not have a known correlation to other adhesion test methods (pull-off, tape, etc.).
4.5 A coating that has a high degree of cohesive strength may appear to have worse adhesion than one that is brittle and hence fractures easily when probed.

5. Apparatus and Materials
5.1 Cutting Tool—Sharputility knife.
5.2 Cutting Guide—Steel or other hard metal straight edge to ensure straight cuts.

6. Test Specimen
6.1 When this test method is used in the field, the specimen is the coated substrate on which the adhesion is to be evaluated.
6.2 For laboratory use, apply the materials to be tested to panels of the composition and surface conditions on which it is desired to determine adhesion.NOTE 2—If desired or specified, the coated test panels may be subjected to a preliminary exposure such as water immersion, salt spray, or high humidity before conducting the knife adhesion test.

7. Procedure
7.1 Select an area free of blemishes and surface imperfec- tions.
7.2 Using a sharp knife and cutting guide, make two cuts into the coating with a 30 to 45 ° angle between legs and...