温度调控下极地菌在EH40钢表面的成膜特性与腐蚀机制研究OA

The work aims to present an original investigation into the temperature-driven bifurcation of microbiologically influenced corrosion(MIC)and microbiologically influenced corrosion inhibition(MICI)on EH40 marine alloy steel.Transcending conventional single-temperature MIC assessments,the distinct regulatory mechanisms are systematically elucidated by which ambient polar temperature(4℃)versus simulated seasonal warming(18℃)dictates biofilm architectural evolution,extracellular polymeric substances(EPS)compositional shifts,and subsequent electrochemical interfacial processes of two representative Arctic marine bacteria:Pseudoalteromonas elyakovii and Halomonas axialensis.To achieve this,a comprehensive micro-to-macro analytical methodology was established.The continuous evolution of the bio-interface was monitored via electrochemical impedance spectroscopy(EIS)to quantify charge transfer dynamics,while the scanning vibrating electrode technique(SVET)was innovatively employed for the in-situ spatial mapping of localized anodic and cathodic micro-galvanic currents across the bio-filmed surfaces.Macroscopic corrosion kinetics were validated through rigorous weight loss measurements over a 14-day exposure period.Furthermore,the spatial architecture of the polar biofilms and the semi-quantitative distribution of key EPS components were resolved with high spatial resolution through multi-color fluorescent staining combined with Confocal Laser Scanning Microscopy(CLSM).Interfacial biomineralization and corrosion product morphologies were systematically characterized through Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy(SEM/EDS),X-ray Diffraction(XRD),and Inductively Coupled Plasma Mass Spectrometry(ICP-MS).The experimental results revealed that elevating the temperature to 18℃significantly accelerated bacterial attachment kinetics and enhanced overall EPS abundance for both strains.However,CLSM and biochemical analyses uncovered a profound,strain-specific bifurcation in their subsequent mechanistic pathways.For P.elyakovii,the temperature shift triggered a fundamental functional reprogramming of its EPS,transitioning from a polysaccharide-dominated matrix at 4℃to a highly proteinaceous network at 18℃.This protein-rich EPS secreted a dense array of active functional groups(notably carboxyl and amino groups)that acted as highly efficient molecular nucleation templates.These templates captured ions from the seawater to induce the rapid,in-situ biomineralization of a compact calcium carbonate(calcite)layer.Rp data demonstrated that this hybrid bio-inorganic composite barrier dramatically elevated the interfacial polarization resistance by 3.2×105 Ω·cm2,effectively acting as a steric shield against the inward diffusion of corrosive species(O2 and Cl-).SVET mapping corroborated this by showing a near-complete suppression of localized anodic current peaks,confirming the onset of MICI.Conversely,the EPS of H.axialensis remained persistently dominated by highly permeable polysaccharides regardless of temperature.At 18℃,its biofilm evolved into a highly clumped,spatially heterogeneous architecture.This extreme non-uniformity established strong localized oxygen concentration cells.SVET analysis dynamically captured the intense micro-galvanic effects induced by this patchy biofilm,revealing highly localized anodic dissolution zones beneath thick biofilm clusters.Consequently,the corrosion morphology fundamentally shifted from the deep,narrow pitting observed at 4℃toward broad,shallow"sheet-like"localized attacks at 18℃,accompanied by a dramatic surge in the macroscopic corrosion rate to 0.22 mm/a.Ultimately,this work establishes a novel biofilm-corrosion mechanistic model,proposing for the first time that environmentally driven shifts in EPS chemistry(specifically the protein-to-polysaccharide ratio)and biofilm spatial heterogeneity are the primary fundamental regulators governing the transition between MIC and MICI.These discoveries provide critical scientific insights for the integrity assessment of structural steels in fluctuating extreme climates and suggest that harnessing specific protein-mediated biomineralizing biofilms could serve as a novel,nature-inspired corrosion control strategy.