1. The characteristics of buried pipelines
1.1 Corrosion characteristics
The corrosion of buried pipelines in urban sewage treatment projects is mainly soil corrosion, which is characterized by scattered pipeline layout and complex soil conditions, so the corrosion mechanism is complex.
Soil corrosion includes electrochemical corrosion and microbial corrosion caused by soil salt, water, oxygen, etc. and steel pipes. Due to the dense urban underground electrical facilities and cables, the corrosion of stray currents is also serious, and the pipelines passing through the factory may even be chemically corroded by acid or alkali media.
1.2 Force characteristics
Urban buried pipelines often pass through roads, buildings, rivers, etc., and the pressure conditions are complex. In addition, the pipeline may be impacted and crushed by sand and gravel during the backfilling process.
1.3 Difficulty in maintenance
Once the buried pipeline is damaged by corrosion, it is not easy to inspect and repair, which will aggravate the corrosion. It often causes environmental damage during maintenance. Due to this feature, the design life of buried pipelines and their anticorrosion is generally required to be above 20-30a.
2, anti-corrosion coating requirements
According to the characteristics of urban buried sewage pipelines, the anti-corrosion layer of the pipeline should meet the following basic requirements:
①Has good chemical resistance;
②Good insulation performance and compactness, preventing corrosion by electrochemistry and stray current;
③Bacterial corrosion resistance;
④It has certain mechanical strength to prevent mechanical damage during handling and burying;
⑤The construction is simple and safe, and meets the requirements of on-site construction.
In addition, there are some special requirements in special areas, such as cold resistance.