Cathodic Protection System Design

It is defined as the degradation or deterioration of a material, usually a metal, due to a reaction with its environment.

What does that mean?

Corrosion is a natural process. Metals don’t like being metals, they prefer remaining as ores.

In the process of converting ores into metals, energy is added in the form of heat, this places the metal into a high-energy state.

It is this energy that is given off from the metal, as the metal is returning to an ore, lower-energy state, is what we call corrosion.

Provide a level of cathodic protection for the entire length of the underground structure. Cathodic protection levels must be controlled so as not to damage coatings.

• Anode

– Metal loss or corrosion occurs at the anode

• Cathode

– Little or no corrosion occurs at the cathode

• Return Circuit/Metallic Path

– Provides a path for electrons to flow, between the anode and cathode

• Electrolyte

– Ionized solution capable of conducting electricity

• Insulating devices must be installed on the steel pipe so as to facilitate electrical isolation.

• Mains – @ Tie-ins and crossings with other utilities

• Services - @ the main and the service riser

• Casings – insulated from the carrier unless both carrier and casing are cathodically protected as a single unit.

• Test leads must be securely attached and minimize stress concentration on the pipe.

• All test lead connections at the pipe must be coated.

• Test leads must extend out of the test box by at least 18”.

• Test box locations and dimensions will be indicated on the design drawings.

• Test leads will be connected as required.

• Bare or coated steel pipe determined to be in areas of continuing corrosion must be cathodically protected.

• Hot Spot Protection.

Pipelines that are exposed to the atmosphere must be cleaned and either coated or jacketed with a material suitable for the prevention of atmospheric corrosion. Steel service risers and meter installations must be coated to the outlet side of the meter bar.

• Exposed Pipe Inspection – Further Investigation if additional corrosion is evident.

• Inspect coatings for damage

• Inspect bare pipe for pitting and uniform wall loss.

• Internal Pipe inspection

• Inspection Data to be kept for the LIFE of the pipe.