Investigation On Corrosion Behavior Of X80 Pipeline Steel In The Presence Of Microorganisms

A large number of engineering materials have been put into use in the marine environments with the increasing demand for exploitation of marine resources.X80 pipeline steel is widely used in marine oil and gas exploitation due to its good toughness and weldability.However,with the extension of the service time,X80 pipeline steel will suffer from serious microbiologically influenced corrosion(MIC)due to the complexity of the seawater environment and the diversity of microbial species.T the service life of the materials is shortened.Therefore,the investigation of microbial corrosion behavior and mechanism of X80 pipeline steel have become one of the hot topics in the field of corrosion and protection research.In this thesis,electrochemical tests(open circuit potential,electrochemical impedance spectroscopy,linear polarization resistance and potentiodynamic polarization curves),weight loss method,observations of biofilm by scanning electron microscope and confocal laser scanning,observation of surface corrosion morphology of samples and X-ray photoelectron spectroscopy of corrosion products were used to systematically study the corrosion behavior of X80 pipeline steel in the presence of microorganisms.The corrosion behavior of X80 pipeline steel in the presence of Pseudomonas aeruginosa,Acetobacter aceti,and Desulfovibrio vulgaris was tested by electrochemical technique.And the calculated Stern-Geary constant(B values)were 35.60 mV,33.00 mV and 58.60 mV,respectively.Therefore,it can be inferred that the Stern-Geary constant of the X80 pipeline steel in the presence of microorganisms is not a fixed value.This research finding helps the linear polarization resistance method to assess the service life of engineering materials accurately,thereby minimizing a series of economic losses and environmental pollution caused by MIC induced material failure.In addition,the research reported that the corrosion rate of X80 pipeline steel under the mixed conditions of Pseudomonas aeruginosa and Acetobacter aceti was accelerated.The corrosion mechanism was the mutual relationship between the pyocyanin and acetic acid secreted by two corrosive bacteria.This research further improved the mechanism of mixed MIC,which promoted the research progress of MIC mechanism,and provided a theoretical basis for fundamentally finding ways to inhibit MIC.