Study On The Performances Of A New Type Of Duplex Stainless Steel With High Resistance To Sulfate Reducing Bacteria Induced Corrosion

Since the coming of 21st century,the marine resource industry has become one of the most important pillars of global economic development.However,corrosion failure of materials is always the most serious problem restricting the development of marine engineering.Marine corrosion environments are complex and harsh.High-salinity seawater and corrosive microorganisms seriously threaten the service safety of marine equipment.Development of high-performance and environmentally friendly materials is significant to the exploitation of marine resources.2205 duplex stainless steel(DSS)is widely used in marine engineering field due to its excellent corrosion resistance in seawater and comprehensive mechanical properties.However,due to its weak resistance to the microbiologically influenced corrosion(MIC),a variety of corrosive bacteria in marine environments,especially sulfate reducing bacteria(SRB),seriously threaten the safety of 2205 DSS.The mechanisms of SRB induced corrosion are complex.Sulfate respiration products of SRB can induce the hydrogen embrittlement(HE)of metals.At the same time,it can also weaken the efficacy of common bactericides and bactericidal ions,which makes the works of corrosion protection more difficult.Based on the interaction mechanism between bactericidal ions,a new type of 2205-Cu-Ce DSS was developed in this study,which can inhibit the SRB induced corrosion effectively.Nano-sized Cu-rich phase(serving as hydrogen trap)precipitated in ferrite phase after aging treatment was designed to improve the resistance to HE and further improve the safety of 2205-Cu-Ce in SRB environments.By analyzing the thermal deformation behaviors,establishing the constitutive equation and drawing the thermal processing diagram,the optimal thermal processing parameters were obtained,which can guide the preparation process of 2205-Cu-Ce DSS.The antibacterial tests revealed that Ce addition exhibited a significant Hormesis effect against SRB.Only when the Ce addition amount reached a critical value(0.18 wt.%in this study),2205-Cu-Ce could effectively inhibit the formation of SRB biofilm.Taking mechanical properties,sweater corrosion resistance and production cost into account,0.18 wt.%Ce addition was determined to be the optimal composition.Compared with 2205 DSS,2205-Cu-Ce(Ce 0.18 wt.%)has almost the same seawater corrosion resistance and higher mechanical properties.Due to the synergistic antibacterial effect of Cu and Ce,2205-Cu-Ce DSS showed a significant inhibitory effect on the SRB induced corrosion.In addition,we found that Cu in 2205-Cu-Ce could only be precipitate diffusely within ferrite grains aging at 700?-1 h.This aging treatment had no damage on the performances of 2205-Cu-Ce DSS,and could efficiently increase hydrogen traps at the high HE sensitive position.Those hydrogen traps in ferrite grains hindered the process of H atoms entering the matrix and diffusing in ?-Fe lattice,which significantly improved the anti-HE performance of 2205-Cu-Ce DSS.Moreover,it was found at other temperatures that the additions of Cu and Ce could inhibit the precipitation of harmful secondary phases such as ?'and ? in 2205 DSS.And that the addition of Cu and Ce increases the activation energy of thermal deformation of 2205 DSS.Ce addition also increased the peak flow stress.The thermal processing diagrams show that 2205-Cu-Ce DSS possesses wide safe processing zones,which indicates its good thermal processing performance.