1. Grade and chemical composition
The grade and chemical composition of the steel for galvanized steel pipes shall comply with the grade and chemical composition of the steel for black pipes specified in GB3092.
2. Manufacturing method
The manufacturing method of the black tube (furnace welding or electric welding) is selected by the manufacturer. Galvanizing uses hot-dip galvanizing.
3.Screw and pipe joint
4.1 For galvanized steel pipes delivered with threads, the threads should be turned after galvanizing. The threads shall comply with the provisions of YB 822.
4.2 Steel pipe joints shall comply with YB 238，malleable cast iron pipe joints shall comply with YB 230.
5. Mechanical properties The mechanical properties of steel pipes before galvanizing shall meet the requirements of GB3092.
6. Uniformity of galvanized layer Galvanized steel pipe shall be used as a test for the uniformity of galvanized layer. The steel pipe sample must not be reddened (copper-plated) for 5 consecutive immersions in the copper sulfate solution.
7. Cold bending test Galvanized steel pipes with a nominal diameter of not more than 50mm shall be subjected to a bending test. The bending angle is 90 °, and the bending radius is 8 times the outer diameter. The test shall be carried without filler, and the weld of the test specimen shall be placed outside or above the bending direction. After the test, there should be no cracks or zinc peeling on the sample.