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, Baowi Steel 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.
Polyurethane Coating
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.
Epoxy Coating
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. Baowi Steel applies epoxy coating in accordance with AWWA C210. Cure times for epoxy coating varies depending on product specified.
Cleaning: The steel pipes are thoroughly cleaned to remove any impurities or residues, ensuring proper adhesion of the zinc coating.
Pickling: The pipes are then immersed in an acidic solution to remove any mill scale or oxides present on the surface. This step further prepares the steel for the galvanizing process.
Galvanizing: The cleaned and pickled pipes are submerged in a bath of molten zinc. Through a metallurgical reaction known as hot-dip galvanizing, the zinc forms a tightly bonded coating on the steel surface.
Cooling and Inspection: After galvanization, the pipes are cooled and inspected for quality control. This step ensures that the zinc coating is uniform and free from any defects.