Applied to the pipe exterior, coatings are the first line of protection against corrosion and other elements. Coatings prohibit corrosion, which can occur from corrosive soils, dissimilar metals, bacteria, stresses, or stray electrical current in the ground. To further the long performance life of steel pipe, Northwest Pipe offers both dielectric and chemical inhibitor pipe coatings such as polyurethane and tape.
Cement Mortar Coating
Cement mortar provides a highly alkaline environment at the surface of the steel cylinder that chemically inhibits or dramatically reduces the rate of corrosion, commonly referred to as “passivation.” Applied under AWWA C205 conditions, rotating belts apply cement mortar to steel pipe in a high-velocity stream to a slowly rotating and translating steel pipe. Simultaneously, reinforcing steel wire is embedded into the mortar coating. Like cement mortar lining, the strength of the mortar coating adds to the pipe stiffness strength.
Potable and non-potable water, soils with low concentration of chlorides or soluble sulfates, or in conditions without fluctuating water tables or moisture conditions.
Polyurethane coating is a spray-applied bonded dielectric coating, which has excellent water and chemical resistance properties. Applied in a single coat process to meet AWWA C222 standards, polyurethane is tough, resilient, and extremely abrasion resistant. Like polyurethanes lining, polyurethane coating is a resilient coating that cures in minutes.
Direct buried, directional drilled or slipline pipe.
Applied in a thin film to a near-white blast steel surface, epoxy coating is a bonded dielectric coating that provides optimum protection against abrasion, corrosive fluids, and extreme temperatures. Epoxy coating is durable and impact resistant resulting in a coating that will not crack, split, or fracture with impact. Northwest Pipe Company applies epoxy coating in accordance with AWWA C210. Cure times for epoxy coating varies depending on product specified.
Specialty direct buried or pipe exposed to atmosphere.
Cold-applied tape coating system include a two- or three-layer process over a primer adhesive in accordance to AWWA C214 resulting in a multi-layer system that provides a final, uniform protective encasement between 50 and 80 mils of strong, lightweight, and reliable bonded coating. In some applications, engineers opt to specify a cement mortar coating over tape coating for an additional layer of protection.
Direct buried pipe.