As an important component of urban infrastructure, the research on corrosion and anti-corrosion technology of water supply network has been paid close attention. Metal pipe has the advantages of high strength and low price. There are a lot of cast iron pipe and steel pipe in water supply network system.
As far as our country is concerned, the proportion of cast iron pipe, ductile iron pipe, steel pipe and other metal pipes in the current water supply system is about 90%. In the foreign pipe network system, the proportion of cast iron pipe and steel pipe and other metal pipes is relatively high: about 53% in Poland, 56% in the United States, and more than 65% in Italy. Among them, steel pipe and cast iron pipe account for the highest proportion in large cities. In Warsaw and sbruck, for example, steel pipes and cast iron pipes account for 91% and 93% respectively.
The inner wall of water supply pipeline contacts with the transmission medium. After a long time of operation, the environmental medium transported continuously impacts and erodes the inner wall of the pipeline, and has complex physical, chemical and biological reactions with the inner wall of the pipeline, resulting in continuous corrosion of the pipe wall. The corrosion products produced in this process accumulate continuously on the inner surface of the pipeline and form nodules.
On the one hand, it hinders the water delivery of the pipeline, resulting in the decline of the water delivery capacity of the pipeline and the increase of the energy consumption required in the water delivery process; on the other hand, the continuous corrosion of the pipeline will cause the inner wall of the pipeline to become thinner, and the pipeline strength will become lower, and even lead to the pipeline perforation and cracking, resulting in the occurrence of pipe leakage and pipe burst, resulting in serious waste of water resources and huge economic losses .
It is found that due to pipeline leakage, more than 32 billion m3 of drinking water is lost in the world every year, accounting for 35% of the total water supply. Taking the data of 2010 "statistical yearbook of urban construction" as an example, the total leakage water volume in China is 62.7552 × 108 m3, equivalent to the annual domestic water consumption of 1.40 × 108 people. Some developed countries, such as the United States, Japan and other countries, the leakage rate of the pipeline network is also very alarming, which is more than 15% and about 25% respectively.
The corrosion of water supply pipe not only causes a lot of waste of water resources and shortens the service life of pipes, but also worsens the quality of drinking water and seriously affects the safety of people's living water. After the corrosion products of cast iron pipe and other metal pipes are released to the water supply network, they can re precipitate to form nodules and adhere to the inner wall of the pipeline.
The surface structure of the nodule is loose, which can not only continue to release iron and its oxides to the water supply network, leading to the occurrence of "yellow water" and "red water" events, but also react with chlorination disinfection by-products, nitrate or natural organic matter in water, resulting in deterioration of water quality of pipe network and secondary pollution of drinking water quality. As a result, the iron content in the effluent of the user terminal is too high, bacteria and turbidity exceed the standard, which seriously affects people's water safety and threatens people's health. Therefore, in order to control the leakage of pipe network and ensure the safety of drinking water quality, it is urgent to study the anti-corrosion technology of water supply pipeline.