Study On Corrosion Of Underground Metal Seamless Pipeline In ShenZhen City

Due to the corrodibility of soil and roughness of corrosion protection presently, old fuel gas pipes in Shen Zhen suffer severe corrosion, confronting a great deal of accidents after more than ten years' running. Therefore, protection to the old fuel gas pipes is indispensable.This dissertation analyses corrodibility factors detailedly of soil circumstance in Shen Zhen, bonding research results of soil corrodibility in the world. Based on mellowed electrochemistry theory, the author conduct exams to soil circumstance and pipe corrosion in Shen Zhen, opining that most of the old fuel gas pipes belong to electrochemistry corrosion. This is the firm theoretical basis for corrosion protection of old fuel gas pipes.Now, corrosion protection method to underground pipes is "double layer protection" principally, namely coating protection connecting negode protection. Based on detecting old fuel gas pipe material, corrosion condition, soil corrodibility and corrosion mechanism ,this dissertation posed coating protection method that polythene gummed tape preservation layer can be used to the old pipes and polythene interlayer preservation layer can be used to new pipes. Furthermore, it posed concrete surface treatment, smearing method, winding manner of polythene gummed tape and some critical proceedings during execution.According to electrochemistry theory, electrochemistry protection is divided into anode protection and negode protection. In proportion to corrosion protection theory and practice in the world, underground pipes should take negode protection. Based on different soil corrosion factors and pipe corrosion principle, obligated current negode protection and sacrifice anode protection can be used here. In the light of theory and application, the author raised that sacrifice anode protection could be used on old fuel gas pipes in Shen Zhen city, and also raised the choice of sacrifice anode, detailed process calculation, the design of ground bed, execution method and detection management. This dissertation took engineering design to the old fuel gas pipes in Shen Zhen city, and pointed out the necessity and feasibility of protection to the old fuel gas pipes. Moreover, a practical and detailed technique scheme is posed. All of these havepositive significance and driving effect to the corrosion protection of old fuel gas pipes in Shen Zhen city.