Application of spray polyurethane (urea) technology in hydraulic wear and corrosion resistance

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In hydraulic anti-corrosion and wear-resistant applications, spray-painted polyurea and polyurethane-urea materials exhibit excellent resistance to chemicals, salt spray, seawater, and atmospheric aging. They have been used worldwide as wear-resistant coatings for truck beds, concrete sealing coatings, wear-resistant coatings for mining equipment and machinery, anti-corrosion coatings for chemical storage tanks, coatings for pool linings and floor waterproofing, as well as for anti-corrosion purposes in marine and water-based facilities and pipelines. The excellent wear and corrosion resistance of spray-painted polyurea and polyurethane-urea make them suitable for use as anti-abrasion materials and anti-corrosion coatings in water engineering. Impact-resistant materials: Many structures used for water discharge and energy dissipation in dams, such as spillways, flood discharge tunnels, overflow dams, and water outlet holes, are subject to erosion and wear caused by high-speed water currents as well as water containing sediment. Significant amounts of labor and financial resources must be invested each year to carry out repairs on these structures. To resist the abrasion of concrete, high-performance concrete and fiber-reinforced concrete are used as materials for dams or tunnels, while epoxy resin mortars and coatings, acrylic mortar or concrete are employed as wear-resistant surface layers. Certain high-performance concretes and abrasion-resistant technologies have achieved good results, but they also have certain limitations. For example, although epoxy resin coatings have high strength, their wear resistance is inferior to that of polyurethanes and polyureas; moreover, they have low elasticity and are prone to cracking. Polyurethane and polyurea materials possess excellent toughness and wear resistance. Polyurethane elastomer wear-resistant linings are widely used in fields such as mining and construction as dry-state anti-wear and wet-state anti-sediment wear coatings, such as linings for slurry pumps and wear-resistant linings for concrete mixers, with remarkable results. There are already reports in China on the use of polyurethane elastomers for anti-scour protection in hydraulic structures. Compared with other protective coating technologies, spray-painted polyurea and spray-painted polyurethane-urea offer high application efficiency, short curing times, high strength and adhesion, good elasticity, a smooth surface, and reduced friction; they represent a new type of impact-resistant material. By spraying polyurethane-urea on high-performance concrete and acrylic mortar surfaces, a wear-resistant composite layer is formed, resulting in an even more optimal resistance to abrasion. Anticorrosive and rust-removing coatings based on sprayed polyurethane and sprayed polyurea exhibit excellent corrosion resistance in harsh environments such as acids, alkalis, salts, oils, water, as well as in extreme cold conditions, underground, or at sea. This is due to their high adhesion, good elasticity, and resistance to hydrolysis; the coatings contain no organic solvents, are continuous, dense, and seam-free, and allow for a thick coating layer to be formed in just one application. As a result, these materials have broad application prospects in areas such as the lining of chemical storage tanks, tunnels, pickling tanks, electroplating tanks, sewage treatment plants, buried oil (gas, water) pipelines, marine steel structures, and bridges spanning seas (rivers). Polyurea and polyurethane-based coatings are used for anticorrosive purposes in hydraulic applications, mainly on two types of substrates: concrete, for its anticorrosive and waterproofing properties, and steel structures, for their anticorrosive and rust-preventing effects. There is a large amount of steel structure in water conservancy projects. Advances in water resources and hydropower technology, such as water conveyance pipelines, gates, steel vessels, water monitoring facilities, bridges, etc., mean that some of these structures are exposed to water for long periods of time, while others are subjected to alternating conditions of being wet and dry. This makes them highly susceptible to oxidation and corrosion, leading to damage. To extend their service life, it is necessary to apply anti-corrosion treatments. For example, large-diameter water transfer pipes for reservoirs manufactured by Northwest Pipe Company in the United States and lined with spray-polyurea showed, after 2 years of use, that the steel surface lining over a length of 20,000 units was intact and retained its excellent performance. In the widening project of the San Mateo Bridge in San Francisco Bay, California, USA, 297,000 square meters were covered with a spray-painted polyurea protective coating. In a domestic project, polyurethane-urea was sprayed on the surfaces of the treated steel gates and frames. After more than 3 years, the surfaces remained smooth and intact, without any cracks, bulging, or peeling, and there was no rust formation, demonstrating its excellent sealing and protective properties. The Marine Chemical Engineering Research Institute conducted experiments on resistance to water flow erosion and seawater corrosion on steel plates coated with polyurea, in seawater at a flow rate of Qiaonai S. The results showed that the polyurea coating exhibited excellent resistance to erosion and corrosion, whereas the ordinary steel plates in the control group suffered significant wear and damage. .