## 4 Corrosion Protection Measures
### Anticrovise Coating
#### 4.1.2 Inorganic Nonmetal Anticorrosive Coating  
At present, pipeline corrosion is mainly prevented using organic coatings. However, due to aging and deterioration, heat resistance, and cold resistance of organic coatings, the service life of pipelines coated with these coatings is limited; therefore, inorganic corrosion prevention technologies have emerged. Compared with organic corrosion prevention coatings, the variety of inorganic, nonmetallic corrosion-resistant coatings is limited. Currently, there are mainly inorganic corrosion-prevention materials used in engineering applications, such as cement mortar corrosion-resistant coatings and concrete corrosion prevention coatings, ceramic corrosion-resistant coatings, enamel corrosion prevention coatings, and glass corrosion prevention coatings. (1) Cement mortar and concrete anticorrosive coating  
In urban pipe networks, cement lining with a thickness of 5 mm is a common anti-corrosion method. Moreover, in underwater pipeline facilities such as rivers and river bottoms, concrete with a thickness of 5-25 mm is commonly used as the counterweight layer and outer mechanical protection layer of the pipeline. However, there are also restrictions on the use of this anticorrosive coating. Generally speaking, cement is alkali-resistant but not acid-resistant because the basic components of cement, tricalcium aluminate, and C4 AF, easily react with acids [97]. The barbed wire mesh or steel skeleton in the concrete anticorrosive coating makes the concrete anticorrosive coating have gaps, so they easily corrode when encountering media such as water and NaC. The volume of the steel bar becomes larger after corrosion, and the stress makes the concrete protective layer crack [98]. Therefore, it is mostly used in pipes with hard water or non-aqueous medium. (2) Ceramic coating  
Ceramic materials are composed of compounds of metal elements, such as alumina, magnesia, zirconia, etc. Ceramic materials may include bricks, stone, coarse ceramics, porcelain, concrete, refractory materials, glass, etc. Ceramics are resistant to high temperature and wear and can be made into finished products resistant to various strong corrosive media. Combined with various modern coating technologies, it is possible to use ceramics as anticorrosive coatings [99]. [PERSON] invented a ceramic coating method, where sanding is carried out before the coating is applied to the alumina ceramic body so that the coating can reach maximum adhesion and strength during the coating process; finally, polishing is carried out, thus avoiding delamination between the coating and the ceramic body as much as possible. The modern preparation method can also be applied to protect ceramic coatings on metal pipelines. Ceramic anticorrosive coating is a kind of high corrosion-resistant anticorrosive coating with high-temperature resistance and very good wear resistance. However, the ceramic anticorrosive coating has poor impact resistance and is not suitable for prefabricated outer anticorrosive coating of steel pipes in buried pipeline engineering in the general sense. Therefore, ceramic coatings are generally only used for internal corrosion protection of process pipelines and process equipment in chemical industries or special environments and are rarely used for external corrosion protection. (3) Enamel coating  
Enamel is a kind of glass-like porcelain layer closely combined with metal, which is obtained by coating enamel on the surface of a metal and then \"enameling\". The traditional enamel process is technically perfect, and the coating is generally used as an internal and external anticorrosive coating for pipelines. However, the \"enameling\" process requires high temperatures of up to 900 degrees Celsius; at this temperature, some steel products will undergo changes in their metal structures. Therefore, enameling is generally only used as an anticorrosive coating on low-carbon steel and other high-temperature-resistant steel products.