Examination of Two Pieces of Pipe from an Oil Well. 1. Introduction 1.1 A request was received for an examination to be carried out on the subject pieces of pipe. 1.2 The examination requested was to determine the overall condition of the pieces of pipe after a period of service and to identify the mechanism responsible for any corrosion damage found. 2. Examination Results 2.1 For report purposes, the subject pieces of pipe were identified as 1 and 2. Pipe 1 was a piece of casing tube approximately 820 mm (32 in) long, 180 mm (7 in) OD and 157 mm (6.2 in) ID which was threaded at one end. It was reported to be from joint 5. Pipe 2 was a piece of tube approximately 775 mm (30.5 in) long, 78 mm (3 in) OD and 62 mm (2.5 in) ID tube, also threaded at one end. It was reported to be from joint 90. Both pieces of pipe were reported to be in the 'as pulled" condition. 2.2. Pipe 1 2.2.1 General examination of Pipe 1 in the as received condition showed that the unthreaded length was coated externally overall with a thin, loosely adherent black gritty deposit containing some red iron oxide. Under this deposit there were some regions of light pitting corrosion. After solvent cleaning however, the original non-metallic protective coating was visible in many places. The thread was free from corrosion products. 2.2.2 Detailed examination showed that there were three deep corrosion pits, approximately in line and close to each other around the circumference of the pipe adjacent to the inner end of the screwed region (see Plate 01). The largest of these pits had perforated the tube wall (see Plate 02). The immediately adjacent threaded material was free from corrosion right up to the lips of the pits, particularly the one which had perforated the wall (see Plates 02 to 05 inclusive). All the pits were sharp edged and the two shown on Plate 1 had tunnelled slightly under the position where the joint sleeve had terminated and formed a lip (see Plates 03 and 05). 2.2.3 Examination of the inner wall of the tubing in the pitted region (Para. 2.2.2.) showed that a liquid had been flowing through it. From the direction of flow, it was evident that the pipe was from the lower end of a pipe section (see Plate 06). 2.2.4 A longitudinal section was cut radially across the pipe wall approximately through the longitudinal axis of the pit shown on Plate 04. The piece thus removed was encased in polymethyl-methacrylate so that the longitudinal sawn face could be prepared for metallographic examination. 2.2.5 After cutting back to a 3 micron finish, the section (Para. 2.2.4.) was examined in both the unetched and etched conditions. The material was found to be clean and the corrosion present was transgranular. 3. Conclusions 3.1 It is considered that the corrosion pits present in the wall of Pipe 1 were the result of crevice corrosion, the crevice being between the inner surface of the end of the joint sleeve and the outer surface of the pipe. 3.2 It is also considered that Pipe 2 was virtually corrosion free.