Appearance Inspection
The coating shall have a smooth appearance with uniform color, free from bubbles, cracks, and shrinkage pores. Slight orange peel texture is acceptable.
Coating Thickness Inspection
Leak Detection
The leaks in the corrosion protection layer shall be inspected using an online electric spark leak detector with a test voltage of 25KV. No leaks are considered acceptable. If there are two or fewer leaks in a single pipe, they shall be repaired according to the provisions of GB/T 23257-2009. If there are more than two leaks in a single pipe or a single leak exceeds 300mm in axial dimension, the pipe shall be deemed unqualified.
Peel Strength Test
Equipment Preparation: Tensile testing machine, portable peel strength testing device, dynamometer, steel ruler, cutting knife, and temperature measuring instrument. The laboratory peel test shall comply with the specifications in Appendix K of GB/T 23257-2017.
Cathodic Disbondment Strength
The required equipment includes an adjustable DC regulated power supply, constant temperature device, magnetic measuring instrument, electric spark leak detector, vernier caliper, plastic cylinder, auxiliary electrode, reference electrode, and sodium chloride solution. The test specifications and operations shall comply with Appendix D of GB/T 23257-2017 or Appendix B of SY/T 0413-2002.
Tensile Strength and Elongation at Break Test for Polyethylene Layer
Samples of the polyethylene layer shall be taken for every 50km of continuously produced corrosion-resistant pipes. The tensile strength and elongation at break shall be tested according to the requirements of the "Plastics - Determination of tensile properties" CB/T 1040. The results shall comply with the provisions in Table 2. If the results are unqualified, one more sample can be taken; if still unqualified, the batch of corrosion-resistant pipes shall be deemed as defective.
Impact Resistance Test
Equipment Preparation: Impact testing machine, including an impact hammer and a vertical guide tube for the impact hammer. Additionally, an electric spark leak detector and a magnetic thickness gauge are required.
