Steel flex piping must be cathodically protected if it is in contact with what?

Cathodic protection is a technique used to prevent corrosion of metal surfaces by making them the cathode of an electrochemical cell. Steel flex piping must be cathodically protected when in contact with backfill material, which is often bare ground. This is because soil can contain electrolytes that promote corrosion, especially when moisture is present. The electrical conductivity of the soil or backfill can accelerate the corrosion process if the steel piping is not adequately protected.

In scenarios where steel flex piping is buried or in contact with moist or corrosive substances in the ground, it's crucial to implement cathodic protection as a preventive measure to ensure the longevity and integrity of the piping system. This protection helps to mitigate the risk of soil-induced corrosion, which can lead to leaks and failures in the pipeline system.

Other options, such as water, air, and concrete, do not directly imply the need for cathodic protection on steel piping in the same way as backfill material. While water can promote corrosion, the requirement for cathodic protection is specifically heightened when the piping is in contact with soil or backfill, where many corrosive chemicals could be present, along with moisture and varying pH levels that contribute to corrosion.