Study On Cathodic Protection Potential Distribution Characteristics Of Large Storage Tanks

The design of oil storage tanks is becoming increasingly large,It is more and more important to design,manufacture and use large storage tanks.Once a leak due to corrosion occurs in the bottom plate of the ground adjacent crude oil storage tanks,it will cause a serious damage to the local environment,and will easily bring about a secondary disaster,which will lead to serious economic losses.The most effective anticorrosion measure for internal and external corrosion of tank bottom is cathodic protection,and analyzing the distribution of cathodic protection potential at bottom of tank is important for preventing corrosion of tank bottom plate.Therefore,Study the distribution of cathodic protection potential of large tank bottom plate,which is very important for improving the cathodic protection effect of tank bottom.This paper takes the PZ petrochemical as the research object,first based on the electrostatic theory,a mathematical model for the cathodic protection potential distribution of the large tank bottom is established.Then the polarization curves of metal Q235 are tested under different conditions.According to the actual state of the tank bottom,Combining with the on-site cathodic protection current density correction,the cathode boundary conditions of the mathematical model were determined.The measured anode polarization curve is used as the anode boundary condition.Select the boundary element method and the Beasy CP software based on the boundary element algorithm are applied to solve the numerical model of tank bottom potential.Based on the measured potential data of PZ Petrochemical large storage tank,the accuracy and validity of the model are verified.For the meshed anode,the concentric flexible anode and the flexible anode clip,study the influence of anode form on the cathodic protection potential distribution of large storage tank,and then,the influence of asphalt resistivity,sand cushion resistivity and soil resistivity on the potential distribution of tank bottom is simulated and analyzed,finally,analyze the influence of the uneven settlement of the tank bottom on the potential distribution.So we can obtain the potential distribution of cathodic protection potential of the large storage tank,and carry out the effectiveness evaluation of cathodic protection system for PZ Petrochemical large storage tank.Numerical simulation results show that:The potential distribution of bottom plate protected by meshed anode is the most uniform,however,the meshed anode requires more protective current than the other two kinds of flexible anodes;the most important influence on the potential of large storage tank is the resistivity of asphalt,following is the sand cushion and soil resistivity;When the tank bottom and asphalt are incomplete fitted,with the change of input current,the potential distribution of the bottom plate protected by the flexible anode is more nonuniform than that of the meshed anode,there may be over protection.By studying the influence of various factors on the potential distribution of tank bottom,we can predict the corrosion of the tank and judge the effectiveness of the cathodic protection system,which is important for reducing the risk of tank bottom corrosion and ensuring the safe operation of tanks.