Corrosion Damage Mechanism And Damage Rate Prediction Methods Investigation Of Gathering Pipelines Steels

Corrosion damage mechanism and corrosion behavior of gathering pipelines steels in Alkaline-Surfactant-Polymer flooding production liquid were first studied in this paper. The corrosion rate of X60 16Mn and 20 steel in ASP flooding production liquid were tested by using static immersing corrosion and erosion. The electrochemistry corrosion behaviors of these steels in ASP flooding medium were studied by electrochemistry polarization curve. The corrosion scales morphology was observed by scanning electron microscope. The chemical composition of corrosion scales was analyzed by X-ray diffraction. The corrosion damage mechanism of these steel in ASP flooding medium were concluded finally by adopting these research methods.When these steels were immersed in static ASP flooding medium, the corrosion rate is increased with the temperature rising and decreased with time process. When the fluid velocity below 1m/s and temperature below 42℃, the average corrosion rate will increase with the fluid velocity and temperature rising. When the fluid velocity above 1m/s, the average corrosion rate will decrease with the temperature rising. At the beginning of corrosion, medium flow will make the corrosion rate accelerate. With the increase of the temperature and fluid velocity, the corrosion rate will decrease due to forming compact corrosion scales, meanwhile, the pitting corrosion tendency will increase. The main composition of corrosion scales is Fe3O4 by the analysis of X-ray diffraction.The other part of the experimentation in the paper is metallic samples test in local ASP flooding experimental station of the Daqing oilfield. The metallic samples will be taken out from pipeline and container at different time span and then measure the corrosion rate and analyze the corrosion scales.The intent of this paper is to build a rapid prediction method of corrosion rate. Basing on different corrosion damage mechanism and calculating the impact factor of oil and oxygen content, average corrosion rate prediction model will be built. Computer curve fitting method will be adopted to predict average corrosion rate.