Representative metallographic specimens were removed from the as-received elbow section for metallurgical evaluation using light optical microscopy and scanning electron microscopy combined with microchemical analysis employing a windowless X-ray detector. Inductively coupled plasma-atomic energy spectroscopy (ICP-AES) and combustion calorimetry (CC) were used to determine the chemical composition of the carbon steel used in the application and specimens were etched in 3% Nital solution to reveal its characteristic microstructure. Grinding was carried out using Buehler abrasive discs down to 600 grit size followed by final polishing using nylon cloth with 9 μm and then 3 μm diamond paste. Both X-ray fluorescence and diffraction were used to analyze samples of the corrosion product removed from the inner surface in the vicinity of the pinhole using JEOL elemental analyzer JSX-3201 (capable of detecting elements down to sodium) and JEOL JDX-3530 X-ray diffractometer system, respectively. The mechanical was evaluated by surface hardness measurement using Vicker's hardness tester.