GB/T 5270-2005 Metallic coatings on metallic substrates?Electrodeposited and chemically deposited coatings?Revies of methods available for testing adhesion
This standard describes methods of checking the adhesion of electrodeposited and chemically deposited coatings. It is limited to tests of a qualitative nature. Table 2 indicates the suitability of each test for some of the most usual types of metallic coatings. Most of the tests described are capable of destroying both the coating and the article being tested, but some destroy the coating only. Even if the adhesion of the coating is found to be satisfactory on articles not destroyed in testing, it shall not be assumed that the articles are undamaged. For example, the burnishing test (see 2.1) may render an article unacceptable and the thermal shock test (see 2.12) may produce unacceptable metallurgical changes.
This standard does not describe certain tests which have been developed at various times to give a quantitative measure of adhesion of metallic coating to a substrate since such tests require special apparatus and considerable skill in their performance which renders them unsuitable as quality control tests for production parts. Some of these quantitative tests may, however, be useful in research and development work.
When particular methods of adhesion testing are included in International Standards for individual coatings, they should be used in preference to the methods described in this International Standard and should be agreed upon beforehand by the supplier and the purchaser.
2 Test methods
2.1 Burnishing test
If plated parts are subjected to burnishing in a localized area, the deposit will tend to work-harden and absorb frictional heat. If the coating is thin, separation of the coating from the basis metal as blisters will occur under these conditions in areas of poor adhesion.
When the shape and size of the part permit, an area of not more than 6cm2 of the plated surface may be rubbed with a smooth implement for about 15s. A suitable implement is a steel rod 6mm in diameter with a smooth hemispherical end.
The pressure shall be sufficient to burnish the coating at every stroke but not so great as to cut the coating. Poor adhesion is indicated by the appearance of a blister which grows as the rubbing is continued.
If the mechanical properties of the coating are poor, the blister may crack and the coating will peel from the basis metal. This test shall be limited to relatively thin deposits.
