Research On Electrochemical Corrosion Behavior Of Carbon Steel In Flue Gas Environment

With the enhancement of people's environmental protection consciousness and the increasing depletion of crude oil,the technology of developing heavy oil by injecting flue gas has a lot of room to develop.The main components of flue gas are CO₂ and N₂,and CO₂ is easy to dissolve in crude oil,thereby reducing the viscosity of crude oil,thus the flue gas can be injected into oil reservoirs to enhance oil recovery.Moreover,it is an effective way to realize CO₂ capture,utilization and storage?CCUS?,thereby reducing greenhouse gas emissions.However,because there are CO₂ and O₂ in flue gas,the flue gas injected to oil reservoir leads to severe corrosion in pipeline and wellbore.So it is of great significance to study the corrosion mechanism of steels in flue gas and thereby find the solutions to inhibit corrosion.This paper conducted an experimental research on the corrosion mechanism of carbon steels in flue gas by using electrochemical methods like potentiodynamic polarization curve and electrochemical impedance spectroscopy?EIS?.The composition of corrosion product film and surface morphology were analyzed by X-Ray diffraction?XRD?,scanning electron microscope?SEM?and energy dispersive spectroscopy?EDS?,respectively.Besides,the effects of temperature on the corrosion rate of carbon steel in flue gas were studied.Moreover,in order to find the solutions to inhibit flue gas corrosion,the corrosion resistance of corrosion inhibitor and alloy steels in flue gas was examined experimentally.The experiment results show that the anode reaction process includes the anodic dissolution of Fe and the oxidization of Fe²⁺to Fe³⁺in the presence of O₂,while the cathode reaction process includes the oxygenation reaction and hydrogen evolution reaction in acidic condition.The corrosion products were composed of FeCO₃,Fe₂O₃ and FeOOH,making the corrosion product film structure porous.Thus,the corrosion product film provides little protection for matrix.Besides,it was found that temperature had important effects on corrosion rate.In the temperature range of 30?to 90?,the corrosion rate reaches to the peak when the temperature is 60?-that is,the corrosion rate increases with the increase of temperature from 30?to 60?,while it decreases sharply with the increase of temperature from 60?to 90?.In addition,the experiment results illustrate that both of corrosion inhibitor and alloy steels can effectively inhibit the corrosion of flue gas.As alloy steels are expensive while corrosion inhibitors are relatively cheap,comprehensive consideration is needed in order to make wise decision between corrosion inhibitors and alloy steels.