Nowadays, pipelines are the most important transportation artery and researches indicate that the pipelines will be a secure tool for energy transmission for over 50 years, which is more significant for petrochemical, oil, and gas industries. The large part of chemical fluids, especially natural gas, transmits with pipelines. These pipelines manufactured with large pipes that they can bear high pressures about several thousand kilogram per cubic centimeter. The gas pressure is obtained by high pressure station in long distances. The function of gas pipelines is very important and vital; therefore, they have to be safe. But unfortunately, utilization of old pipelines in operation increases probability of occurrence. The most important reasons of making these occurrences are the internal and external corrosions that are very effective in damaging gas pipelines, hence safety decreases. So, controlling of corrosion in gas pipelines needs to use cathodic protection with cathodic potential, substance becomes a cathode, and this system decreases the rate of corrosion. Periodic inspections of pipelines are essential, through a method called pigging. A pig is a device inserted into a pipeline which travels freely through it and is driven by the product flow to do specific tasks within the pipeline. In this paper, first, corrosion and its types, as one of the most important threats in gas pipelines, will be investigated. Then methods of controlling corrosion will be explained by stating that cathodic protection is the most important method. Finally, pigs will be investigated because it needs continuous inspections in the performance of pipelines for security reasons.