Research On Cathode Protecting Technique For Soil Corrosion Of Underground Pipelines In Petrochemical Corporation And Related Application

Material corrosion problem of soil environment is not only the basic subject in corrosion scientific research,but also a practical problem of underground engineering which needs to be solved urgently.The factors that influence the soil corrosion are as follows:soil structure,resistivity,nonhomogeneity,saltness,oxygen content,water content,pH value,temperature,pressure,types of microorganism,oxidation-reduction potential etc.With the development of oil and energy industry,more pipelines of oil,water and natural gas are buried underground.Fire disaster and explosion hazard are possible to happen once the complicated pipelines are leaked,which greatly threat the human safety and lead to the environmental pollution.Therefore,we generally use the protective coating and cathode protection to avoid the corrosion of underground pipelines.The thesis focuses on the experimental study of buried metal test pieces which are corrosive in the refinery,detect the soil environment,and analysis the reasons that caused the corrosion.Design and establish the suitable cathode protection scheme to control the corrosion of pipelines.The following conclusions are made according to the research:1.The resistivity,the water content and the salt content of the soil,together with the sulfate radical,the content of chlorion are the main factors that influence the corrosion of underground pipelines in the refinery.2.Compared with the buried pipeline Q235 steel test block,we find that the one with the cathode protection is better on the corrosion than the one without the protection which means the cathode protection is useful.3.The cathode protection method of the underground pipelines in refineries adopts the coating method,together with the impressed current protection method.Meanwhile,it also uses the auxiliary anode material,buried anode ground bed design,the pressure-sharing technique and on-line monitor of cathode protection parameters.The test result shows that the fully protected buried steel pipelines account for more than 90%in the refinery,which means the cathode protection of underground pipe network has achieved good result and it is infallible to protect the safety.