The length of the needle hole test specimen for coated composite steel pipes is about 1000mm. The coating of the steel pipes is inspected using an electric spark leak detector under the specified test voltage. The coating thickness of the coated composite steel pipe shall not exceed 0.4mm, and the test voltage shall be 1500V. The coating thickness of the coated composite steel pipe is greater than 0.4mm, and the test voltage is 2000V. Check for the generation of electric sparks, and the test results should comply with regulations.