The GB/T 30791-2014 standard specifies in detail the method of T-Bend test for Paints and varnishes on metal substrates to evaluate the flexibility and adhesion of coatings. This test checks how the coating behaves during bending, including whether cracking or flaking occurs, by bending the coating test plate to an angle of 180 °. The standard specifies the test equipment, operation steps and evaluation criteria to ensure the accuracy of the test. The T-Bend test is used to determine the minimum diameter that the coating can withstand during bending to ensure the Reliability and durability of the coating in practical application.