Effect And Mechanism Of Hydrogen-consuming Microorganisms On Cathodic Protected High-strength Steel

High-strength low-alloy(HSLA)steels have the advantages of save resources and reduce costs,but it is susceptible to hydrogen embrittlement(HE).In marine environments,inappropriate cathodic potentials will promote the hydrogen penetrate into steel and lead to HE.If we can utilize the hydrogen consuming microorganisms to consume the hydrogen generated in the process of cathode protection,reducing the amount of hydrogen's penetrating into material,then the potential can be reasonably lowered,making the steel ideally protected to a minimum corrosion rate and reducing the possibility of HE's occurring at the same time.The corrosion behavior of AISI 4135 steel in the presence of hydrogen consuming microorganisms(Blautia coccoides GA-1)was studied in this paper.The results show that strain GA-1 could directly or indirectly obtain electrons from AISI 4135 steel with the maximum current density of-1.54?A/cm² which was not the primary reason leading to the increase of corrosion current.The corrosion rate was positively related to the number of strain cells under free corrosion potential.The hydrogen permeation behavior of AISI 4135 steel in the presence of strain GA-1 was studied and the hydrogen consuming ability of strain GA-1 was characterized by hydrogen permeation efficiency(?).The results show that the adherent strain GA-1cells could obtain the newly generated[H]directly from the vicinity of the cathode surface and reducing the hydrogen concentration and decreasing the?.Strain GA-1could reduce the?by about 9%under-0.85V vs.SCE polarization potential.A more negative cathodic potential(-1.05V vs.SCE)inhibits strain GA-1's attaching to the cathode surface,leading to weaker hydrogen consumption effects and the?was basically unchanged.Strain GA-1 can effectively consume cathodic hydrogen and decrease hydrogen permeation current when a smaller constant polarization current(-3?A/cm²)was applied.The increased total hydrogen permeation in 8 d was only0.47×10^-6 mol/cm².The stress corrosion cracking(SCC)susceptibility was measured by slow strain rate test(SSRT).The results show that both cathode protection and strain GA-1 can increase the HE susceptibility(I_scc)of AISI 4135 steel.I_scc increased by more than 40%compared with the free corrosion potential conditions.Although the strain GA-1 can consuming cathodic hydrogen and reducing the?,the apparent HE susceptibility of AISI 4135 steel is also increased due to its side effects.Therefore,the key to inhibiting HE is to enhance the effect of consuming cathode hydrogen and reduce the side effects of strain GA-1.The corrosion,hydrogen permeation and mechanical behavior of AISI 4135 steel in the presence of hydrogen consuming microorganisms was studied systematically in this project.The feasibility of using hydrogen consuming microorganisms to inhibit hydrogen embrittlement of HLSA steel was analyzed.The realization of this method is of great significance for the safe application of HLSA steel in marine environments,having broad application prospects.