Corrosion Behavior Of 2205 Duplex Stainless Steel In Typical Atmospheric Tower Environment Was Studied

2205 duplex stainless steel(2205DSS)was widely used in gas and oil industry due to their perferable corrosion resistant and mechanical property.The research of corrosion mechanism of 2205DSS in oil refining corrosion environment became important when the exposed serious corrosion problems.The methods for this paper include that weight loss method,potentiodynamic polarization curves,cyclic polarization curves and Electrochemical Impedance Spectroscopy(EIS),Scanning Kelvin Probe(SKP),Scanning Electron Microscopy(SEM),X-ray Energy Dispersive Spectrometer(EDS)and X-ray Photoelectron Spectroscopy(XPS),etc.First of all,the corrosion mechanism of 2205DSS in oil phase and aqueous phase was studied according to the production medium of HuiZhou refinery.The results showed that resistance of 2205DSS is stable in blank oil phase,which little effect form temperature and acid value.The corrosion rate of 2205dss is biggest in second atmospheric fraction and lewest in desalted crude oil.Meanwhile studied the effect of S and Cl in oil phase,the result reflected that S and Cl have significate role in corrosion acceleration of 2205DSS.Secondly,the corrosion mechanism of 2205DSS in HCl + Na2S aqueous solution was studied on the basis of former simulation corrosion experiment.The results showed that the competitive adsorption of HS-,H2S and OH-on passivation film in HC1 solution,so the pitting was promoted(except Na2S content below 30 mg/L).For another,the role of HS-,H2S is disparate in HCl solutions of different concentration:When the HCl concentration was 3.60 g/L,30 mg/L Na2S had an inhibitory effect on corrosion,100 mg/L Na2S promote the dissolution of the passive film which lead to pitting corrosion.And when the concentration of HC1 was 5 g/L,30 mg/L Na2S will greatly promote the general corrosion of 2205DSS.Finally,the pitting corrosion resistance of 2205DSS in NaCl solution was studied.The results showed that the critical pitting temperature of 2205DSS in NaCl 35 g/L solution is between 40? to 60?.pH value has little effect on pitting corrosion resistance of 2205DSS.The pitting corrosion resistance increased with the decrease of concentration of NaCl.In the alkaline NaCl environment,Na2S increases the general corrosion,and restrain the effect of pitting corrosion.However,the addition of Na2S in the neutral NaCl solution can accelerate the dissolution rate of the passive film and decrease the pitting resistnce.