G. Impact test
Cut a sample with a length of about 100mm from any position of the coated steel pipe, and conduct an impact test in an environment with a temperature of (20±5) ℃ to observe the damage of the inner coating. During the test, the weld should be located in the opposite direction of the impact surface.

H. Vacuum test
The length of the test piece of the pipe section is (500±50) mm. Use appropriate measures to prevent the inlet and outlet of the pipe. Gradually increase the negative pressure from the inlet to 660mm Hg and keep it for 1 min. After the test, check the inner coating.

I. High-temperature test
The length of the test piece of the pipe section is (100±10) mm. Place the test piece in a constant temperature box, raise the temperature of (300±5) ℃ and keep it constant for 1 h, then take it out and let it cool to room temperature. After the test, take out the test piece and check the innermost coating (allowing the appearance of darkening and darkening).

J. Low-temperature test
The length of the test piece of the pipe section is (100±10) mm. Place the test piece in a low-temperature box, cool it down to (-30±2) ℃, and keep it constant for 1 h, then take it out and place it at (20±5) ℃ (4~7) h under the environment.

K. Pressure cycle test
Connect with the water pressure supply system, fill with water to remove air, and then carries out 3,000 alternating water pressure tests. The period of each test is not more than 2 s. After the test, check the inner coating and conduct an adhesion test as required.

L. Temperature cycle test
The length of the test piece of the pipe section is (500±50) mm, and the test piece shall be placed under each temperature condition in the following order for 24 h: After the test, the test piece shall be placed in an environment with a temperature of (20±5) ℃ for 24 h. Coating condition, and conduct adhesion test according to regulations.

M. Warm water is aging test
The length of the test piece of the pipe section is about 100 mm. The exposed parts of the pipe section should be treated with corresponding anti-corrosion treatment. The pipe section shall be immersed in distilled water (70±2) ℃ for 30 d. After the test, take it out and let it cool to room temperature. Check the test piece Internal coating.