Cathodic Protection Systems Installations
Underground pipelines defined as ductile iron pipe, cast iron, and galvanized (zinc coated) steel pipe are all susceptible to corrosion via soil and water. The ductile iron pipe industry uses a ‘protected annealing oxide skin of 135 microns,’ this coating, equal to the thickness of a piece of paper, claims to protect against corrosion. Photo evidence proves that a polyurethane and zinc coating on ductile iron pipe is not invincible to scratches and chips- this occurring BEFORE the pipe is even installed underground, possibly during transit while on-loading and off-loading. Even the smallest of scratches can lead to massive corrosion within 15 years, depending on the soil environment. The polyethylene encasement sleeve or “Poly-wrap” used at connection points and applied over-the-ditch can be torn, punctured, improperly sealed, or become unwrapped, allowing the trapped air/water molecules to corrode the junction point. Cathodic protection is not able to penetrate this sleeve, allowing corrosion to go unchecked. Prior to burial, the pipe must be resistant to weathering by the sun and by wind and pollutants in the air, resist thermal expansion during storage in hot summer months, and contraction during cold winter months. The coating must be hard but not crack, chip or peel. Proper preparation of the pipe and application of the coating must be an exact science without fault or the coating will fail.
The oil and gas industry overwhelmingly uses fusion bonded epoxy (FBE) coated steel pipe for the thousands of miles of pipe they install. Cathodic protection is federally mandated in this case due to the high temperature and high pressure the underground pipes must tolerate.
Coatings are the first line of defense against corrosion. In the instance that the coating is compromised, cathodic protection is recommended as a secondary electrical barrier against corrosive soils, rocks, tree roots, and shifting of the earth (Anode Systems has confirmed 21 different instances of compromised pipe systems– read the full list). Working in concert with both polyethylene and FBE protective coatings, cathodic protection by Anode Systems provides a cost-effective solution to expensive leaks.