GB/T 1720-2020Circle-drawing test of coating films (English PDF)

Foreword

This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.

This Standard replaces GB/T 1720-1979, "Method of test for adhesion of paint films". Compared with GB/T 1720-1979, the main technical changes, except editorial changes, are as follows:

-- Change the standard name to "Circle-drawing test of coating films";

-- Add Scope, Normative references, Principle, Sample, Test panel, Test report (see Chapter 1, Chapter 2, Chapter 3, Chapter 5, Chapter 6, and Chapter 9);

-- Modify requirements for the equipment (see 4.1; Chapter 1 of version 1979);

-- Add the schematic diagram of the circle-drawing tester of electric coating films and the dimension figure of the rotating needle (see Figure 2, Figure 3);

-- Add regulations for the rotating needle (see 4.2);

-- Modify the test procedures (see Chapter 7, Chapter 2 of version 1979);

-- Modify requirements for the test panel (see Chapter 6; Chapter 1 of version 1979);

-- Modify the expression of results (see Chapter 8; Chapter 3 of version 1979);

1 Scope

This Standard specifies a test method to evaluate the peeling degree of the coating film from the substrate, when the overlapping cycloid diagram penetrates the coating film to the substrate.

This Standard applies to the determination of circle-drawing test of a single flat coating film on a hard substrate.

The performance that is measured by this experimental test method not only depends on the adhesion of the coating to the substrate, but also on various other factors; so, this test method cannot be regarded as a method for measuring adhesion.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 3186, Paints, varnishes and raw materials for paints and varnishes - Sampling

GB/T 9271, Paints and varnishes standard panels for testing

GB/T 9278, Temperatures and humidity for conditioning and testing of paint specimens

GB/T 13452.2, Paints and varnishes - Determination of film thickness

GB/T 20777, Paints and varnishes - Examination and preparation of samples for testing

GB/T 37356, Paints and varnishes - Lighting and procedure for visual assessments of coatings

3 Principle

Fix the test panel on a test-bed that can be moved forward and backward; while moving the test-bed, the rotating needle in a circular motion penetrates the […]

7 Test procedure

8 Expression of results

Mark seven positions, namely 1, 2, 3, 4, 5, 6, and 7, in turn on the upper side of the cycloid scratch, which are divided into 7 grades, where grade 1 is the […]