Polyurea Anti-Corrosion Coating In Desalination Project

The availability of China’s per capita fresh water resource is only a quarter of the world average. In northern provinces of China, the per capita water resources is even less than500cubic meters. So the shortage of water resources has been the main problem that restricts the development of our economy, especially in northern parts of China. Desalination, the most potential technical solution to solve this problem, will be expected an explosive growth.In desalination, concrete substrate needs to have good anti-corrosion property during the storage and long-distance transport of fresh water. During the early experiments, pure polyureas coating showed good corrosion resistance and had high strength. However, there were also several problems. To begin with, the coating of pure polyurea was easily damaged in low temperature environment, because of embrittlement. Then, adhesive strength between polyurea coatings and concrete substrates was not enough. Furthermore, because of high surface energy of the coating, aquatic organisms adhered and got moldy easily, which resulted deterioration of water quality.In order to solve the problems mentioned above, a novel kind of anti-corrosion coating system was developed successfully, which had long performance life and high reliability, and was easy to use during construction. This system contains three layers, primer, middle layer coating and topcoat. In order to solve the problem of embrittlement, hydroxy-terminated polyether was introduced to polyurea to synthesis a urea/urethane hybrid hard segment. The result showed that when the molar ratio of WANALINK6200and E-100was1:1, and polyurea contained35%hard segment, the modified polyurea had the best tensile strength, proper breaking elongation, good low-temperature resistance and lower loss rate of hydrolysis. So it was suitable to be used as the middle coating. Moreover, in order to improve the adhesive strength between polyurea coating and concrete substrate, polyurethane primer containing silica, an active inorganic filler, was prepared. Experiments showed that adhesive strength was improved effectively after using polyurethane primer containing silica. The addition of silica also improved the hydrolysis resistance and hydrophobicity of primer coating. Finally, this paper evaluated several commercial topcoats, including acrylate-modified polyurethane coating, fluorocarbon topcoat, acrylate topcoat and silicone topcoat. The results showed that silicone topcoat had the best hydrophobic property and the most excellent hydrolysis resistance, which could be used as surface layer.At last, Pilot test was carried out at Caofeidian desalination base using polyurea spray machine, Graco H-XP3. The results indicated that the anti-corrosion coating system investigated in this paper had excellent appearance, waterproof performance, long service life and could be processed conveniently.