One, standard coating thickness for anti-corrosion pipes
The thickness and color of the paint applied to anti-corrosion pipes depend on several factors, and are typically between 120 and 180 μm. The following table provides information on paint types and thicknesses, which should be considered based on the specific application process: Electroplating (GB standard) 6-8 μm, Spray Coating 50-120 μm (depending on the type of plastic powder: flat finish 60-80 μm, textured finish 80-120 μm, sand finish 50-80 μm, high gloss 70-100 μm), and Spray Paint 30-50 μm.
Two. What are the methods for protecting pipes?
1、Coating corrosion protection
Apply a uniform and dense coating of paint to the cleaned metal pipe surface to isolate it from various corrosive media. This is one of the most fundamental methods for pipe corrosion protection. Since the 1970s, the installation of pipes in harsh environments such as polar and marine environments, as well as the heating of oil for transportation, which increases pipe temperature, has placed more demands on coating performance. Therefore, corrosion-resistant pipe coatings are increasingly using composite materials or composite structures.
① Exterior wall anti-corrosion coating: Types and application conditions of coating materials for external wall pipes.
② Inner Wall Corrosion-Resistant Coating: A thin film applied to the inner wall of the pipe to prevent internal corrosion, reduce friction resistance, and increase flow rate. Commonly used coatings include amine-cured epoxy resins and polyamide epoxy resins, with coating thicknesses ranging from 0.038 to 0.2 millimeters. To ensure a strong bond between the coating and the pipe wall, the inner wall of the pipe must be properly treated. Since the 1970s, there has been a trend toward using the same materials for both the inner and outer pipe walls, allowing for simultaneous coating of both.
③ Corrosion and Insulation Coating: On medium and small-diameter pipelines for hot oil or fuel oil, a composite layer is applied to the exterior of the pipeline to reduce heat dissipation to the soil. Commonly used insulation materials are rigid polyurethane foam plastics, with a suitable temperature range of -185 to 95℃. This material has a soft texture, and to improve its strength, a high-density polyethylene layer is applied to the outer side of the insulation layer to form a composite material structure, preventing groundwater from entering the insulation layer.
2、Electrochemical protection
Methods to alter the electrochemical potential of a metal relative to its surrounding medium, thereby protecting it from corrosion. Cathodic protection and electrochemical corrosion prevention are the primary methods used for long-distance pipeline protection.
① Cathodic Protection: A method of preventing metal corrosion by polarizing the metal to be protected into a cathode. This technique, first used in pipelines in 1928, applies the principle of protecting the negative electrode in a metal corrosion cell from corrosion while the positive electrode is corroded. By applying an external current to fully polarize the metal surface in the electrolyte, corrosion is prevented.
② Corrosion Prevention Method: This involves taking measures on facilities with stray currents to minimize leakage current. It also includes avoiding areas with stray currents during pipeline laying, or improving the insulation and corrosion protection of the affected pipe sections, and using shielding and insulating flanges. Furthermore, stray currents are diverted from the affected pipelines back into the power grid where they originate, thereby eliminating the corrosion caused by stray currents. This method can be classified into three types: direct diversion, polarity diversion, and forced diversion, depending on the application range and the performance of the diversion equipment. Many countries have established technical regulations for protecting against alternating current interference voltages, primarily using safety distance and pipe leakage methods to protect the pipes from damage.