Growth in electrical generation sources and greater electrical power demands in North America, drive need for new electric transmission lines with multiple circuits. Many understand a transmission line loading can vary seasonally and increase over time. Typical approaches to address the variation in analyzing AC corrosion is simply using the maximum transmission line loading. In corridors with multiple circuits, the maximum transmission line loading may significantly underestimate the maximum induced voltage on inductively coupled pipelines. Multiple circuits significantly add to the complexity of AC corrosion as variable loading and even power flow direction affect the vectoral summation of magnetic fields. This paper highlights the challenges that engineers will overcome in addressing shared corridors with multiple circuits. This includes the need to understand the phase configuration, power system rotation, power flow, and the importance that engineering tools consider varying induction on shield wires.