Corrosion Inhibition Mechanism of S355J0W Steel Against Desulfovibrio vulgaris and Pseudomonas aeruginosa
Marine environments are extremely harsh and corrosive.Marine corrosion is mostly associated with the metabolic activity of microorganisms.Microbiologically influenced corrosion(MIC)seriously threatens the reliability and safety of marine engineering facilities and restricts the development of the marine economy.Many methods have been applied to prevent MIC in steels,such as coatings,biocides,cathodic protection,and MIC-resistant alloy steels.The development of MIC-resistant alloy steels by adding alloying elements is an important strategy for marine MIC prevention.Exploring MIC mechanisms can provide a theoretical basis for MIC prevention.Therefore,the inhibition mechanism of S355J0W steel,composed of multiple alloying elements(Cr,Ni,Nb,and Cu),on the MIC caused by typical marine corrosive microorganisms(Desulfovibrio vulgaris and Pseudomonas aeruginosa)is investigated using surface analysis,weight loss,and electrochemical tests,with EH36 steel as a control.The results show that D.vulgaris and P.aeruginosa can acquire electrons from the Fe(0)surface and promote steel corrosion through the biocatalytic reduction of sulfate and nitrate reactions by transferring the electrons harvested from steel to intracellular,respectively.Notably,in both the anaerobic medium containing D.vulgaris and the aerobic medium containing P.aeruginosa,S355J0W steel had a much lower MIC rate than EH36 steel.In the D.vulgaris medium,the weight loss and maximum pitting depth of S355J0W steel were 2.9 mg·cm-2 and 50.4 μm,respectively,whereas these values for EH36 steel were 5.2 mg·cm-2 and 71.5 μm,respectively:the weight loss and maximum pitting depth of S355J0W steel were 56％and 70％of those of EH36 steel,respectively.Meanwhile,in the enriched seawater with P.aeruginosa,the weight loss and maximum pitting depth of S355J0W steel were 2.5 mg·cm-2 and 26.3 μm,respectively,and those of EH36 steel were 4.6 mg·cm-2 and 56.2 μm,respectively:the weight loss and maximum pitting depth of S355J0W steel were 54％and 47％of those of EH36 steel,respectively.In addition,S355J0W steel exhibited higher Rp and Rct values.The weight loss,pitting depth,and electrochemical data confirmed that S355J0W steel has better MIC resistance.Compared to EH36 steel,S355J0W steel contains Cr,Ni,Nb,and additional Cu.On the one hand,the alloy elements in S355J0W steel make the corrosion product film on its surface more protective,with a higher membrane resistance value.In addition,the combined effect of alloying elements on grain refinement can improve the anti-corrosion properties of steels.This can also explain why the corrosion resistance of S355J0W steel is better than that of EH36 steel.By contrast,the sessile D.vulgaris and P.aeruginosa cell counts on the S355J0W steel surface were only 22％and 24％,respectively,of those on the EH36 steel surface,owing to the combined effect of the alloying elements.The extracellular electron transfer(EET)rate is usually the controlling step for corrosion rates;fewer sessile cells lead to a lower EET rate,which reduces the MIC rate of S355J0W steel.Notably,the planktonic cell counts of the two steels did not significantly differ,suggesting that the planktonic D.vulgaris and P.aeruginosa cell counts are not critical in contributing to the difference in corrosion rates.At present,the MIC-resistant properties of metal materials are mainly improved through the addition of Cu,and research is mainly focused on stainless steels.Few studies have been conducted on the effects of the joint action of multiple alloying elements on the MIC-resistant properties of marine structural steels.Therefore,the results of this study are expected to provide new insights into the design and development of MIC prevention strategies for marine structural steels.
alloy elementsmicrobiologically influenced corrosion(MIC)Desulfovibrio vulgarisPseudomonas aeruginosaextracellular electron transfer(EET)
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