Anti-corrosion treatment of the inner wall of metal conduit in buried engineering: large-diameter pipeline is directly sandblasted for anti-corrosion, small-diameter pipeline is derusted and pickled, and cloth is bound with a long stick when brushing, and repeated construction.

The anticorrosion method of anticorrosion steel pipe is generally to use paint for anticorrosion. Let's take a look at the knowledge of coating anticorrosion.

Coating anticorrosion is one of the most basic methods of steel pipe anticorrosion, which is to coat the coating evenly and densely on the surface of derusted metal pipeline to isolate it from various corrosive media. More and more composite materials or composite structures are used for anticorrosion coating of steel pipes. These materials and structures should have good dielectric properties, physical properties, stable chemical properties and wide temperature adaptation range.

1. External wall anticorrosion coating: types and application conditions of external wall coating materials for pipelines.

Inner wall anticorrosive coating: a thin film coated on the inner wall of pipeline to prevent pipeline corrosion, reduce friction resistance and increase transportation capacity. The commonly used coatings are amine cured epoxy resin and polyamide epoxy resin, and the thickness of the coating is 0.038 ~ 0.2 mm In order to ensure the firm combination of the coating and the pipe wall, the inner wall of the pipe must be surface treated. Since 1970s, there has been a tendency to use the same material to coat the inner and outer walls of pipelines, so that the coating of the inner and outer walls of pipelines can be carried out at the same time.

Anti-corrosion and thermal insulation coating: In order to reduce the heat loss of the pipeline to the soil, a thermal insulation and anti-corrosion composite layer is added to the outside of the medium and small diameter pipeline for transporting crude oil or fuel oil. The commonly used thermal insulation material is rigid polyurethane foam, and the applicable temperature is-185 ~ 95℃. This material is soft. In order to improve its strength, a layer of high density polyethylene is added outside the insulation layer to form a composite structure to prevent groundwater from infiltrating into the insulation layer.

2. If the outer protective tube is a polyethylene tube, there is no need for anticorrosion.

Polyethylene is odorless and nontoxic, feels like wax, and has excellent low temperature resistance (the lowest service temperature can reach -70 ~- 100℃), good chemical stability, resistance to most acids and bases (oxidation-resistant acids), insolubility in general solvents at room temperature, and low water absorption. However, as a linear molecule, it can slowly dissolve in some organic solvents without swelling, and has excellent electrical insulation performance.