Recent failure analyses of several modern pipelines in oil service have exhibited pin-hole leaks at the 6 o’clock position. The pits formed on the inside surface from a combination of pitting corrosion and under deposit corrosion. Two case studies involving an 8-inch and a 12-inch OD API 5L Grade X52M pipeline are discussed. The work scope for the pipeline failure analyses included visual examination, metallography, energy dispersive X-Ray spectroscopy (EDS) of corrosion products, X-Ray diffraction (XRD) analysis, Vickers hardness and tensile tests to determine the mechanism that led to the perforation(s). The failure analyses results indicated that the pitting corrosion likely occurred from the presence of free water and salts, while under deposit corrosion occurred from a layer of deposits containing paraffin, sand, salts and iron oxides. Pipelines anticipated to have significant accumulation of internal deposits require frequent internal cleaning via pigging and the subsequent use of corrosion inhibitors to improve pipeline integrity.