This process standard applies to the corrosion protection of equipment and steel pipes used in civil and general industrial construction. Corrosion is a destructive phenomenon caused by the chemical and electrochemical effects of the surrounding medium. Corrosion can be categorized into internal and external wall corrosion based on the location of the steel pipe; general and localized corrosion based on the corrosion type; and chemical and electrochemical corrosion based on the corrosion mechanism.
The corrosion protection process for construction steel pipes is as follows: surface preparation → coating preparation → application of intermediate coating → painting or spraying → maintenance.
1. Steel pipe corrosion protection is divided into main body corrosion protection and welded joint corrosion protection.
2. The material used for steel pipe corrosion protection depends on the material used for the main steel pipe anti-corrosion coating.
3. Common joint patching methods include petroleum asphalt joint patching, coal tar epoxy joint patching, adhesive tape joint patching, powder epoxy joint patching, and PE heat shrinkable joint patching. 4. If the main body of the steel pipe is a three-layer PE composite structure, the preferred patching material is a three-layer PE heat shrink patching material.
5. The patching of the single-layer epoxy powder coating can be done in three ways: epoxy powder, adhesive tape + primer, and three-layer PE heat shrink patching.
The domestically used steel pipe anti-corrosion layers include petroleum asphalt, PE jacket and PE foam jacket, epoxy coal tar, coal tar enamel, epoxy powder, and three-layer composite structure, epoxy coal tar cold wrap (PF type), rubber-plastic epoxy coal tar cold wrap (RPC type), etc. At present, the most widely used steel pipe anti-corrosion methods are the three-layer PE composite structure, single-layer powder epoxy, PF-type cold wrap, and RPC-type cold wrap.
(1) Petroleum asphalt, the raw materials are widely available, and the price is low. However, the working conditions are poor, the quality is difficult to guarantee, and the environmental pollution is serious.
(2) Epoxy coal tar is easy to operate, but the coating takes a long time to cure, is greatly affected by the environment, is not suitable for field operations, and is difficult to construct below 10°C. (3) Epoxy powder anti-corrosion, using electrostatic spraying, has good fusion bonding with the pipe body of the same material and strong adhesion, but epoxy powder has poor waterproofness (high water absorption rate, reaching 0.83%), which brings certain difficulties to cathodic protection design. It requires high-quality equipment on site, is difficult to operate, and is difficult to control quality.
(4) 3PE heat shrink material, steel pipe anti-corrosion sealing, high mechanical strength, strong waterproofness, stable quality, convenient construction, good applicability, and no pollution to the environment. PE has a low water absorption rate (less than 0.01%), and at the same time has high epoxy strength, low PE water absorption, and good hot melt adhesive softness, etc., with high anti-corrosion reliability. The disadvantage is that compared with the cost of other patching materials, the cost is high.
(5) PF and RPC cold wraps are simple and easy to install. The three matching setting glues make PF-type epoxy coal tar cold wraps suitable for installation in any environment, any season, and any temperature conditions. Cold wrap and 3PE heat shrink tape are suitable for steel pipes with a main corrosion coating made of various materials, while other methods are suitable for steel pipes with a main corrosion coating made of the same or similar materials.
Secondly, with development, some steel pipes also require insulation while undergoing corrosion protection. Petroleum is a complex mixture that easily corrodes steel pipes, making corrosion protection essential. However, refined oil pipelines also require insulation while undergoing corrosion protection. In Northeast China and during winter, thermal expansion and contraction can cause freezing and cracking of steel pipes, impacting stable supply.
Process Steel Pipe Corrosion Protection Methods
Coating: One of the most basic methods for steel pipe corrosion protection is to apply a coating evenly and densely to the surface of a rust-removed steel pipe to isolate it from various corrosive media. Since the 1970s, laying steel pipes in harsh environments such as polar regions and oceans, as well as the elevated temperatures of steel pipes caused by heated oil transportation, have placed greater demands on coating performance. Consequently, steel pipe anti-corrosion coatings are increasingly using composite materials or composite structures.
① External Wall Anti-Corrosion Coating: The types of materials and application conditions for the external wall coating of steel pipes. ② Inner wall anti-corrosion coating: A thin film applied to the inner wall of a steel pipe to prevent corrosion, reduce friction, and increase throughput. Common coatings include amine-cured epoxy resins and polyamide-epoxy resins, with a coating thickness of 0.038 to 0.2 mm. To ensure a strong bond between the coating and the pipe wall, the inner wall of the pipe must be surface-treated. Since the 1970s, there has been a trend toward using the same material for both inner and outer pipe coatings, allowing for simultaneous coating of both surfaces.
③ Anti-corrosion and thermal insulation coating: On medium- and small-diameter steel pipes used for hot transportation of crude oil or fuel oil, a composite insulation and corrosion-resistant layer is applied to the exterior of the pipe to reduce heat loss from the pipe to the soil. The commonly used insulation material is rigid polyurethane foam, suitable for temperatures between -185°C and 95°C. This material is soft in texture, and to enhance its strength, a high-density polyethylene layer is applied over the insulation layer to create a composite structure that prevents groundwater from seeping into the insulation layer.
Post time: Sep-16-2025