Before the pipeline is tested all welds will have been inspected for defects by ultrasonic or radiographic techniques. The operator will carry out an on line inspection using an inspection tool, known as a pig, which is propelled inside the pipeline by the gas flow. The first inspection will take place early in the life of the pipeline and at scheduled intervals afterwards.

Corrosion is a normal occurrence common to all metals not in their natural state. The process often results in the deterioration of the metal. In many cases the metal deterioration can be severe enough to warrant replacement or repair. A simple scientific explanation for corrosion is that it's an electrochemical process and very similar to a battery where electrons flow between anodic (negative) and cathodic (positive) contacts. For corrosion to occur four elements are required: Anode: The area of deterioration or site from which corrosion occurs and current flows Cathode: The area of protection or site from which no corrosion occurs and current flows Electrolyte: A medium capable of conducting electric current (i.e. soil, water or concrete) Metallic Path: Connection between the anode and cathode

Cathodic Protection (CP) is a technology used to protect buried or immersed metals from corrosion. It is defined as the reduction or elimination of the corrosion process by either making the corroding metal a cathode via an impressed direct current (DC) or by connecting it to a sacrificial or galvanic anode. Impressed current cathodic protection: This type of cathodic protection system requires an external power source (AC, solar) and is typically applied to metal structures with large surface areas such as transmission pipelines or above grade storage tanks. Galvanic cathodic protection: This type of cathodic protection system is self-powered and is the simplest application of cathodic protection. Typically it is applied to metal structures in a soils environment where there is limited exposed surface area (i.e. well-coated short distance pipelines). Alternately, can also be used for large uncoated structures in sea water application.

CP has been in use for decades to protect underground pipelines, ship hulls, offshore oil and gas production platforms, underground steel storage tanks, interior submerged portions of tanks and many other structures that are exposed to marine or corrosive environments.