GB/T 43658.1-2024 "Nondestructive Testing, Pipeline Corrosion and Sediment X and Gamma Ray Testing, Part 1: Tangential Radiographic Testing" specifies the basic technical requirements for tangential radiographic testing using film and digital radiography techniques. This standard applies to the detection of defects such as point corrosion, surface corrosion and erosion caused by steel pipes during service, including cylindrical objects such as small bore tubes, pressure tubes, boiler drums and Pressure Vessels. This paper describes the evaluation method of pipeline material loss caused by corrosion or erosion, and specifies the techniques for detecting and measuring thickness loss in wall thickness direction, which are suitable for industrial film radiography, computer radiography (CR) and digital array detector (DDA).