The buried pipeline anti-corrosion layer includes the overall anti-corrosion layer of the steel pipe and the joint anti-corrosion layer at the welding joint. Specific main features include:

    1 Good electrical insulation The corrosion of underground pipelines is an electrochemical process. The corrosion battery circuit is composed of pipelines and the surrounding soil. The insulation of the corrosion protection layer directly determines whether the corrosion current is generated and its value. At the same time, the insulation of the anti-corrosion layer is also the basic condition for preventing stray current interference and corrosion. The electrical insulation indexes of the anticorrosion layer commonly used in pipeline anticorrosion are: volume resistivity, surface resistivity, electrical strength and insulation resistance.

    2 Adhesion force Adhesion force is the most basic performance of anti-corrosion layer. Corrosive media such as water vapor need to contact the metal substrate through the interface between the anti-corrosion layer and the coated object. The strong bonding force can maintain the stability of this interface, avoid the accumulation of moisture under the anti-corrosion layer due to penetration, and prevent the corrosive medium in the anti-corrosion layer. It is enriched to prevent corrosion under the film and blistering of the paint film.

     3 Anti-breathability The underground environment through which the pipeline passes is very complicated, and the environment may be very humid or have groundwater. The low water permeability or low water absorption rate of the anticorrosive layer is closely related to the high insulation properties of the anticorrosive layer; the corrosion reaction depends on the penetration and diffusion of the corrosive medium to the anticorrosive layer. The transmission and supplementation can effectively prevent various forms of corrosion.

     4 Good durability and resistance to soil corrosion Because underground pipelines are semi-permanent facilities, maintenance and repair are very difficult, and the cost is quite high, so the pipeline anti-corrosion layer must be able to withstand the soil corrosion environment and maintain long-term stability.

     5 Mechanical strength and resistance to soil stress The steel pipe is a long process from coating construction to installation to the ground, which may be subjected to many mechanical forces, such as collision. Friction, etc., must also withstand the effects of changes in ambient temperature, requiring the anti-corrosion layer to be impact-resistant, wear-resistant and flexible, so as to minimize the damage of the anti-corrosion layer. In cohesive soils, due to changes in soil moisture, stress will be exerted on the anti-corrosion layer; the expansion and contraction of the pipeline due to temperature changes will cause the soil to shear the anti-corrosion layer of the pipeline. Therefore, the anti-corrosion layer should have the ability to resist soil stress.

     6 The quality of the supporting pipeline anti-corrosion layer is the sum of the quality of the pipeline anti-corrosion layer and the quality of the anti-corrosion layer. There is only a good tube anti-corrosion layer, there is no reliable anti-corrosion layer technology, and the pipeline anti-corrosion layer also fails. . Anticorrosion layer defects may occur in the production of anticorrosion layer. The damage of the anticorrosion layer in the pipeline construction process is difficult to avoid. It has an impact on the integrity of the anticorrosion layer. The repair anticorrosion layer and the original anticorrosion layer should be well combined, and the anticorrosion performance is equivalent, so that the anticorrosion layer has integrity.

     7 Matching with cathodic protection Most underground pipelines, especially large pipelines, special ring pipelines need to adopt anticorrosion measures that combine anticorrosion layer and cathodic protection.

      8 Storage stability pipeline construction has a period of time. The anticorrosion steel pipe may have to be transported for a long distance, stored for a long time, and the pipe is exposed. This requires the anticorrosion layer to have stable performance, be able to withstand the influence of the atmospheric environment, and be resistant to thermal aging and light. Ageing.

地下管道防腐层主要的性能要求

埋地管道防腐层包括了钢管整体的防腐层以及焊口处的补口防腐层。具体主要的性能包括了：

   1 良好的电绝缘性   地下管道的腐蚀是一个电化学过程，腐蚀电池回路是由管道以及其周围的土壤构成的，防腐层的绝缘性好坏，直接决定了腐蚀电流是否产生及其数值大小。同时，防腐层的绝缘性也是防止杂散电流干扰和腐蚀的基本条件。管道防腐常用的防腐层电绝缘指标为：体积电阻率、表面电阻率、电气强度和绝缘电阻。

   2 黏结力    黏结力是防腐层最基本的性能。水汽等腐蚀介质需要通过防腐层和被涂物体之间的界面而接触金属基体，黏结力强可以保持此界面的稳定，避免水汽因渗透作用而在防腐层下富集，防止腐蚀介质在防腐层下得富集从而防止膜下腐蚀和漆膜起泡。

    3 抗透气性   管线所经过的地下环境非常复杂，所处环境可能很潮湿或有地下水。防腐层渗水性低或者说低吸水率与防腐层的高绝缘性质紧密相关；腐蚀反应的进行有赖于腐蚀介质对防腐层的渗透和扩散，抗透气性抗渗透性好的防腐层能够阻止腐蚀介质的传递和补充，有效防腐各种形式腐蚀。

    4 良好的耐久性、耐土壤腐蚀性    由于地下管道属于半永久性的设施，维护和维修都很困难，且成本代价相当高，所以管道防腐层必须能够承受土壤腐蚀环境，保持长期稳定。  

    5 机械强度以及耐土壤应力作用    钢管从涂敷施工到安设到地下，是时间比较长的一个过程，可能要经受许多机械力的作用，如碰撞。摩擦等，也要经受环境气温变化的作用，要求防腐层抗冲、耐磨并具有柔韧性，以使防腐层的损伤降低到最低限度。在黏性土壤中，由于土壤干湿变化，将对防腐层产生应力；管道因温度变化而膨胀与收缩，导致土壤对管道防腐层形成剪切作用。因此防腐层应当具有耐土壤应力的能力。

    6 补口补伤的配套性   管线防腐层的质量是管体防腐层质量和补口防腐层质量的总和，只有好的管体防腐鄫，没有可靠的补口防腐层技术，管线防腐也是失败的。防腐层生产中可能有防腐层缺陷产生，管道建设过程中防腐层损伤很难避免，对防腐层完整性产生影响，应当有简便易行得方法对防腐层进行修补。修补防腐层和原防腐层应结合良好，防腐性能相当，使防腐层具有完整性。

    7  和阴极保护的匹配性    大多数地下管道，特别是大型管道，特殊戒指管道需要采用防腐层和阴极保护相结合的防腐措施。

     8 储存稳定性   管道建设有一个时间周期，防腐层钢管可能要经过长距离运输过程，长时间存储，布管暴露，这就要求防腐层性能稳定，能够经受大气环境的影响，抗热老化、光老化。