Corrosion prevention measures for carbon steel pipes
Thread Content
Carbon steel pipes have poor corrosion resistance, but due to their strong pressure tolerance and good workability, they are also widely used in buried pipelines. Therefore, its anti-corrosion measures have become a key focus in the project. Currently, the main technologies used for external anti-corrosion of buried steel pipes include petroleum asphalt anti-corrosion coatings, coal tar enamel anti-corrosion coatings, polyethylene adhesive tape anti-corrosion coatings, fused epoxy powder anti-corrosion coatings, two-layer polyethylene anti-corrosion coatings, and three-layer polyolefin anti-corrosion coating technologies. Here, we will mainly introduce the anti-corrosion coating technology for polyethylene adhesive tapes. The anti-corrosion system for polyethylene adhesive tape consists of a primer, an inner anti-corrosion layer, and an outer protective layer. Anti-corrosion coatings are classified into different grades; depending on the pipe diameter, environment, anti-corrosion requirements, and construction conditions, different coating structures and thicknesses are selected. The anti-corrosion layer of polyethylene adhesive tape boasts excellent water resistance and oxidation resistance, a low moisture absorption rate, good insulation properties, resistance to cathodic disbonding, impact resistance, and a wide temperature range; it maintains stable performance within a temperature range of 30–80°C. The anti-corrosion performance of polyethylene adhesive tape mainly depends on the adhesion at the adhesive-film interface. By using a solvent-free adhesive and hot-press bonding technology to bond the polyvinyl film in a heated state with the solvent-free adhesive under certain pressure, the polyvinyl adhesive tape can achieve strong and stable adhesion, ensuring the quality of the anti-corrosion layer. The main disadvantages of the anti-corrosion layer made of polyethylene adhesive tape are its poor resistance to soil stress; especially at high temperatures, poor adhesion combined with high density leads to cathodic shielding.
Carbon steel pipes buried underground are prone to corrosion, so anti-corrosion measures are particularly important. Common methods used nowadays include petroleum asphalt, epoxy powder, polyethylene adhesive tape, and several others. Here, we will focus on the method of making polyethylene adhesive tape. It generally has three layers: first, a primer is applied; then an internal anti-corrosion tape is wrapped; and finally, an external protective tape is applied. The exact thickness to use and the way of wrapping it depend on the diameter of the pipe, the installation environment, and the anti-corrosion requirements. This type of tape has many advantages: it is water-resistant, does not age easily, provides good insulation, and is impact-resistant. It can function stably in temperatures ranging from minus 30 degrees to 80 degrees. The quality depends on whether the glue and film stick well together. Currently, hot-pressing technology is commonly used to press polyethylene film and solvent-free adhesives together, resulting in a strong bond and stable corrosion resistance. However, it also has disadvantages, mainly its weak resistance to soil pressure. At high temperatures, the adhesion strength decreases and cathode shielding issues may arise; special attention must be paid to this during construction. .