The Study Of Temperature Effect On Corrosion And Cathodic Protection Of Typical Pipeline Steel In Soil

Pipeline steel is widely used in our country.It is mainly used in petroleum,petrochemical and natural gas pipeline system,as well as oil and gas wells and gas storage wells in various oilfields.However,the corrosion is very harmful to the material.A prominent feature of service conditions of pipeline steel is the temperature variation.So the design of reasonable cathodic protection technology will be used to provide reliable protection of pipeline operation.This paper simulated the soil environment of different temperature and humidity,and studied the influence of temperature and humidity of soil environment steel on cathodic protection potential and hydrogen evolution potential of 16Mn steel and X65by electrochemical test.Through their corrosion morphology under different temperature and humidity conditions,and compare with corrsion mechanism,behaviour which can provide a significant reference for practical engineering practice to select the appropriate parameters of cathodic protection,the results shows behind:In the corrosion behavior of the research process:corrosion morphology characterized by weight loss after the experiment,we can see two steels corrosion morphology no significant difference in the same soil moisture,and pitting corrosion under low humidity conditions,general corrosion under high humidity conditions.The corrosion potential and the corrosion current density in the soil environment were obtained by the polarization curves,and the corrosion potential was in negative trend with increasing temperature.The corrosion behavior of the two kinds of pipeline steel is similar.The reason may be that the steel all belong to low-alloy structural steel,The corrosion behavior of the material is mainly affected by the environmental factors.In the study of protection potentials,the results of polarization curves show that the protective potentials tend to shift negatively with increasing temperature.By comparison with the hydrogen permeation potential,it can be seen that the protection potentials of the two steels are positive than hydrogen permeation potential,so that the protection potential is suitable for the environment.Starting from 40?"-0.85V_CSE standard"is not suitable at higher temperatures.The results show that the anode area of the two steels appears to be diffusion-controlled with the increase of humidity and temperature,which may be due to the accumulation on the surface of X65 steel and 16Mn steel to form a mixed structure of soil and corrosion products.Under the anodic polarization condition,Ion diffusion,and diffusion at high temperatures is weakened,which may be due to the reduced stability of the mixed structure and the accelerated ion diffusion rate.In the study of the hydrogen permeation potential,the hydrogen permeation potentials of 16Mn steel and X65 steel in different soil environments and at different temperatures were obtained by analyzing the characteristics of EIS,the potential of hydrogen evolution in each soil environment showed a negative shift trend.The experimental results of X65 steel in NaCl solution?wt=3.5%?show that the diffusion coefficient of hydrogen will decrease with increasing temperature,and the measured hydrogen permeation current density increases obviously,The hydrogen permeation potential does shift negatively with increasing temperature,and the hydrogen concentration of hydrogen on the surface of the X65 steel increases.