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Microbial corrosion (MIC) yog ib qho teeb meem loj hauv ntau lub lag luam, vim nws tuaj yeem ua rau poob nyiaj txiag loj.Super duplex stainless hlau 2707 (2707 HDSS) yog siv nyob rau hauv marine ib puag ncig vim nws cov tshuaj tiv thaiv zoo heev.Txawm li cas los xij, nws qhov kev tawm tsam rau MIC tsis tau sim ua kom pom.Txoj kev tshawb no tau tshuaj xyuas tus cwj pwm ntawm MIC 2707 HDSS tshwm sim los ntawm cov kab mob marine aerobic Pseudomonas aeruginosa.Electrochemical tsom xam pom tau hais tias nyob rau hauv lub xub ntiag ntawm Pseudomonas aeruginosa biofilm nyob rau hauv 2216E nruab nrab, ib tug zoo hloov nyob rau hauv lub corrosion muaj peev xwm thiab ib tug nce nyob rau hauv corrosion tam sim no ceev.Kev soj ntsuam ntawm X-ray photoelectron spectroscopy (XPS) pom qhov txo qis hauv Cr cov ntsiab lus ntawm qhov chaw ntawm cov qauv hauv qab biofilm.Kev tsom xam pom ntawm cov pits tau pom tias P. aeruginosa biofilm tsim qhov siab tshaj plaws qhov tob ntawm 0.69 µm thaum 14 hnub ntawm incubation.Txawm hais tias qhov no me me, nws qhia tau tias 2707 HDSS tsis muaj kev tiv thaiv tag nrho rau MIC ntawm P. aeruginosa biofilms.
Duplex stainless hlau (DSS) yog dav siv nyob rau hauv ntau yam kev lag luam vim yog kev sib xyaw ua ke zoo tshaj plaws ntawm cov khoom siv kho mob zoo heev thiab kev tiv thaiv corrosion 1,2.Txawm li cas los xij, hauv zos pitting tseem tshwm sim thiab cuam tshuam rau kev ncaj ncees ntawm cov hlau no 3,4.DSS tsis tiv taus microbial corrosion (MIC) 5,6.Txawm hais tias muaj ntau yam kev siv rau DSS, tseem muaj ib puag ncig uas qhov kev tiv thaiv corrosion ntawm DSS tsis txaus rau kev siv mus ntev.Qhov no txhais tau tias cov ntaub ntawv kim dua uas yuav tsum tau muaj kev tiv thaiv corrosion ntau dua.Jeon et al7 pom tias txawm tias super duplex stainless hlau (SDSS) muaj qee qhov kev txwv ntawm kev tiv thaiv corrosion.Yog li ntawd, nyob rau hauv tej rooj plaub, super duplex stainless hlau (HDSS) yuav tsum tau ntau dua corrosion kuj.Qhov no coj mus rau txoj kev loj hlob ntawm high alloyed HDSS.
Corrosion resistance DSS nyob ntawm qhov piv ntawm alpha thiab gamma theem thiab depleted nyob rau hauv Cr, Mo thiab W cheeb tsam 8, 9, 10 nyob ib sab mus rau theem ob.HDSS muaj cov ntsiab lus siab ntawm Cr, Mo thiab N11, yog li nws muaj kev tiv thaiv corrosion zoo heev thiab tus nqi siab (45-50) ntawm qhov sib npaug pitting tsis kam (PREN) txiav txim los ntawm wt.% Cr + 3.3 (wt.% Mo + 0.5 wt. .% W) + 16% wt.N12.Nws zoo heev corrosion kuj nyob ntawm seb muaj pes tsawg leeg uas muaj kwv yees li 50% ferritic (α) thiab 50% austenitic (γ) theem.HDSS muaj cov khoom siv kho tshuab zoo dua thiab siab dua rau cov tshuaj chloride corrosion.Kev txhim kho corrosion kuj txuas ntxiv kev siv HDSS nyob rau hauv ntau chloride ib puag ncig xws li marine ib puag ncig.
MICs yog ib qho teeb meem loj hauv ntau qhov kev lag luam xws li roj thiab roj thiab dej kev lag luam14.MIC tso nyiaj rau 20% ntawm tag nrho cov kev puas tsuaj corrosion15.MIC yog bioelectrochemical corrosion uas tuaj yeem pom hauv ntau qhov chaw.Biofilms uas tsim rau ntawm qhov chaw hlau hloov cov txheej txheem electrochemical, yog li cuam tshuam cov txheej txheem corrosion.Nws yog dav ntseeg tias MIC corrosion yog tshwm sim los ntawm biofilms.Electrogenic microorganisms noj tawm cov hlau kom tau txais lub zog uas lawv xav tau kom muaj sia nyob17.Cov kev tshawb fawb MIC tsis ntev los no tau pom tias EET (extracellular electron hloov) yog qhov txwv tus nqi hauv MIC vim yog cov kab mob electrogenic.Zhang et al.18 pom tau hais tias electron intermediaries ua kom lub cev hloov ntawm cov hluav taws xob ntawm Desulfovibrio sessificans hlwb thiab 304 stainless hlau, uas ua rau MIC hnyav dua.Anning et al.19 and Wenzlaff et al.20 tau pom tias biofilms ntawm cov kab mob corrosive sulfate-txo cov kab mob (SRBs) tuaj yeem nqus cov electrons ncaj qha los ntawm cov hlau substrates, uas ua rau muaj qhov hnyav heev.
DSS paub tias yuav raug rau MIC hauv xov xwm uas muaj SRBs, cov kab mob uas txo cov hlau (IRBs), thiab lwm yam. 21 .Cov kab mob no ua rau thaj chaw pitting ntawm DSS nyob rau hauv biofilms22,23.Tsis zoo li DSS, HDSS24 MIC tsis paub zoo.
Pseudomonas aeruginosa yog kab mob Gram-negative, motile, qws-zoo li tus kab mob uas yog dav faib nyob rau hauv xwm25.Pseudomonas aeruginosa kuj yog ib pawg microbial loj nyob rau hauv ib puag ncig marine, ua rau siab MIC concentrations.Pseudomonas nquag koom nrog hauv cov txheej txheem corrosion thiab tau lees paub tias yog ib tus neeg ua haujlwm pioneer thaum lub sij hawm tsim biofilm.Mahat et al.28 and Yuan et al.29 pom tau hais tias Pseudomonas aeruginosa nyhav nce qhov corrosion ntawm me me hlau thiab alloys nyob rau hauv dej ib puag ncig.
Lub hom phiaj tseem ceeb ntawm txoj haujlwm no yog txhawm rau tshawb xyuas cov khoom ntawm MIC 2707 HDSS tshwm sim los ntawm cov kab mob marine aerobic Pseudomonas aeruginosa siv cov txheej txheem electrochemical, cov txheej txheem tshuaj xyuas saum npoo thiab cov khoom siv tshuaj tiv thaiv corrosion.Electrochemical kev tshawb fawb, suav nrog qhib Circuit Court muaj peev xwm (OCP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), thiab muaj peev xwm dynamic polarization, tau ua los kawm txog tus cwj pwm ntawm MIC 2707 HDSS.Lub zog dispersive spectrometric tsom xam (EDS) tau ua los xyuas cov tshuaj lom neeg ntawm qhov chaw corroded.Tsis tas li ntawd, X-ray photoelectron spectroscopy (XPS) tau siv los txiav txim siab qhov ruaj khov ntawm oxide zaj duab xis passivation nyob rau hauv kev cuam tshuam ntawm ib puag ncig marine uas muaj Pseudomonas aeruginosa.Qhov tob ntawm lub pits tau ntsuas nyob rau hauv lub confocal laser scanning microscope (CLSM).
Table 1 qhia cov tshuaj muaj pes tsawg leeg ntawm 2707 HDSS.Table 2 qhia tau hais tias 2707 HDSS muaj cov khoom siv zoo heev nrog lub zog tawm ntawm 650 MPa.Ntawm daim duab.1 qhia qhov kho qhov muag microstructure ntawm kev daws cov cua sov kho 2707 HDSS.Nyob rau hauv lub microstructure uas muaj txog 50% austenite thiab 50% ferrite theem, elongated bands ntawm austenite thiab ferrite theem tsis muaj theem nrab pom.
Ntawm daim duab.2a qhia qhov qhib Circuit Court muaj peev xwm (Eocp) piv rau lub sijhawm raug rau 2707 HDSS hauv 2216E abiotic nruab nrab thiab P. aeruginosa broth rau 14 hnub ntawm 37 ° C.Nws qhia tau hais tias qhov kev hloov loj tshaj plaws thiab tseem ceeb tshaj plaws hauv Eocp tshwm sim hauv thawj 24 teev.Qhov txiaj ntsig Eocp hauv ob qho tib si nce siab ntawm -145 mV (piv rau SCE) nyob ib puag ncig 16 h thiab tom qab ntawd poob qis, nce mus txog -477 mV (piv rau SCE) thiab -236 mV (piv rau SCE) rau cov qauv abiotic.thiab P Pseudomonas aeruginosa daim coupon, ntsig txog).Tom qab 24 teev, Eocp 2707 HDSS tus nqi rau P. aeruginosa kuj tseem nyob ruaj khov ntawm -228 mV (piv rau SCE), thaum tus nqi sib thooj rau cov qauv tsis yog tshuaj lom neeg yog kwv yees li -442 mV (piv rau SCE).Eocp nyob rau hauv lub xub ntiag ntawm P. aeruginosa yog heev tsawg.
Kev tshawb fawb Electrochemical ntawm 2707 HDSS cov qauv hauv abiotic nruab nrab thiab Pseudomonas aeruginosa broth ntawm 37 ° C:
(a) Eocp raws li kev ua haujlwm ntawm lub sijhawm raug, (b) polarization nkhaus ntawm hnub 14, (c) Rp ua haujlwm ntawm lub sijhawm raug, thiab (d) icorr ua haujlwm ntawm lub sijhawm raug.
Table 3 qhia txog cov kab mob electrochemical corrosion ntawm 2707 HDSS cov qauv uas raug rau abiotic thiab Pseudomonas aeruginosa inoculated media nyob rau lub sijhawm 14 hnub.Cov tangents ntawm lub anode thiab cathode nkhaus tau extrapolated kom tau txais kev sib tshuam muab corrosion tam sim no ceev (icorr), corrosion muaj peev xwm (Ecorr) thiab Tafel nqes hav (βα thiab βc) raws li tus qauv txoj kev30,31.
Raws li qhia hauv daim duab.2b, kev hloov pauv ntawm P. aeruginosa nkhaus ua rau muaj kev nce hauv Ecorr piv rau abiotic nkhaus.Tus nqi icorr, uas yog proportional rau tus nqi corrosion, nce mus rau 0.328 µA cm-2 nyob rau hauv cov qauv Pseudomonas aeruginosa, uas yog plaub npaug ntau dua nyob rau hauv cov qauv tsis-biological (0.087 µA cm-2).
LPR yog ib qho classic uas tsis yog kev puas tsuaj electrochemical rau kev tshawb xyuas corrosion ceev.Nws kuj tau siv los kawm MIC32.Ntawm daim duab.2c qhia qhov polarization tsis kam (Rp) ua haujlwm ntawm lub sijhawm raug.Tus nqi Rp ntau dua txhais tau tias tsawg dua corrosion.Hauv thawj 24 teev, Rp 2707 HDSS peaked ntawm 1955 kΩ cm2 rau cov qauv abiotic thiab 1429 kΩ cm2 rau Pseudomonas aeruginosa specimens.Daim duab 2c kuj qhia tau hais tias tus nqi Rp tau txo qis sai tom qab ib hnub thiab tom qab ntawd tseem tsis tau hloov pauv li ntawm 13 hnub tom ntej.Tus nqi Rp ntawm tus qauv Pseudomonas aeruginosa yog kwv yees li 40 kΩ cm2, uas yog qis dua li 450 kΩ cm2 tus nqi ntawm cov qauv uas tsis yog tshuaj lom neeg.
Tus nqi ntawm icorr yog proportional rau lub uniform corrosion tus nqi.Nws tus nqi tuaj yeem xam los ntawm cov kab zauv hauv qab no Stern-Giri:
Raws li Zoe et al.33, tus nqi ib txwm ntawm Tafel txoj kab nqes B hauv txoj haujlwm no tau muab coj los ua 26 mV / dec.Daim duab 2d qhia tau hais tias qhov icorr ntawm cov qauv uas tsis yog-biological 2707 tseem nyob ruaj khov, thaum cov qauv P. aeruginosa hloov pauv tau zoo heev tom qab thawj 24 teev.Cov txiaj ntsig icorr ntawm P. aeruginosa cov qauv yog ib qho kev txiav txim siab ntau dua li cov kev tswj tsis yog lom.Cov qauv no zoo ib yam nrog cov txiaj ntsig ntawm polarization tsis kam.
EIS yog lwm txoj kev uas tsis muaj kev puas tsuaj uas siv los ua cov tshuaj tiv thaiv electrochemical ntawm qhov chaw corroded.Impedance spectra thiab xam capacitance qhov tseem ceeb ntawm cov qauv raug rau abiotic ib puag ncig thiab Pseudomonas aeruginosa tov, passive zaj duab xis / biofilm tsis kam Rb tsim rau ntawm tus qauv nto, them nqi hloov Rct, hluav taws xob ob txheej capacitance Cdl (EDL) thiab tas li QCPE Phase element tsis (CPE).Cov kev ntsuas no tau txheeb xyuas ntxiv los ntawm kev ua kom haum cov ntaub ntawv siv tus qauv sib npaug (EEC).
Ntawm daim duab.3 qhia txog Nyquist plots (a thiab b) thiab Bode plots (a' thiab b') rau 2707 HDSS cov qauv hauv abiotic media thiab P. aeruginosa broth rau ntau lub sijhawm incubation.Txoj kab uas hla ntawm Nyquist nplhaib txo qis thaum muaj Pseudomonas aeruginosa.Cov phiaj xwm Bode (Fig. 3b') qhia qhov nce ntawm tag nrho impedance.Cov ntaub ntawv hais txog lub sijhawm so tas li tuaj yeem tau txais los ntawm theem maxima.Ntawm daim duab.4 qhia cov qauv ntawm lub cev raws li monolayer (a) thiab bilayer (b) thiab cov EECs sib thooj.CPE tau nkag mus rau hauv EEC qauv.Nws qhov kev lees paub thiab impedance tau qhia raws li hauv qab no:
Ob lub cev qauv thiab sib npaug sib npaug circuits rau haum lub impedance spectrum ntawm tus qauv 2707 HDSS:
qhov twg Y0 yog tus nqi KPI, j yog tus lej xav lossis (-1) 1/2, ω yog qhov ntau zaus, n yog KPI lub zog ntsuas tsawg dua ib qho 35.Tus nqi hloov pauv tsis kam inversion (piv txwv li 1 / Rct) sib raug rau tus nqi corrosion.Qhov me Rct, qhov siab dua qhov corrosion ntawm 27.Tom qab 14 hnub ntawm incubation, Rct ntawm Pseudomonas aeruginosa cov qauv mus txog 32 kΩ cm2, uas yog ntau npaum li cas tsawg tshaj li 489 kΩ cm2 ntawm non-biological kuaj (Table 4).
Cov duab CLSM thiab SEM cov duab hauv daim duab 5 qhia meej tias cov txheej txheem biofilm nyob rau saum npoo ntawm HDSS qauv 2707 tom qab 7 hnub yog ntom.Txawm li cas los xij, tom qab 14 hnub, cov ntaub ntawv biofilm tsis zoo thiab qee lub hlwb tuag tshwm sim.Table 5 qhia txog biofilm thickness ntawm 2707 HDSS kuaj tom qab kis tau P. aeruginosa rau 7 thiab 14 hnub.Qhov siab tshaj plaws biofilm thickness hloov ntawm 23.4 µm tom qab 7 hnub rau 18.9 µm tom qab 14 hnub.Qhov nruab nrab biofilm tuab kuj tau lees paub qhov qauv no.Nws poob ntawm 22.2 ± 0.7 μm tom qab 7 hnub rau 17.8 ± 1.0 μm tom qab 14 hnub.
(a) 3-D CLSM duab ntawm 7 hnub, (b) 3-D CLSM duab ntawm 14 hnub, (c) SEM duab ntawm 7 hnub, thiab (d) SEM duab ntawm 14 hnub.
EMF nthuav tawm cov tshuaj lom neeg hauv biofilms thiab cov khoom siv corrosion ntawm cov qauv raug rau P. aeruginosa rau 14 hnub.Ntawm daim duab.Daim duab 6 qhia tau hais tias cov ntsiab lus ntawm C, N, O, thiab P nyob rau hauv biofilms thiab corrosion khoom yog ho siab dua nyob rau hauv cov hlau ntshiab, vim hais tias cov ntsiab lus no txuam nrog biofilms thiab lawv cov metabolites.Cov kab mob tsuas xav tau cov kab mob chromium thiab hlau xwb.Cov qib siab ntawm Cr thiab Fe hauv cov khoom siv biofilm thiab cov khoom siv corrosion nyob rau saum npoo ntawm cov qauv qhia tias cov hlau matrix tau poob cov ntsiab lus vim yog corrosion.
Tom qab 14 hnub, pits nrog thiab tsis muaj P. aeruginosa tau pom nyob rau hauv nruab nrab 2216E.Ua ntej incubation, qhov saum npoo ntawm cov qauv yog du thiab tsis muaj teeb meem (Daim duab 7a).Tom qab incubation thiab tshem tawm cov khoom siv biofilm thiab corrosion, qhov tob tshaj plaws ntawm qhov chaw ntawm cov qauv raug kuaj xyuas siv CLSM, raws li qhia hauv daim duab 7b thiab c.Tsis muaj qhov pom tseeb pitting tau pom nyob rau saum npoo ntawm kev tswj tsis yog lom (qhov siab tshaj pitting qhov tob 0.02 µm).Qhov siab tshaj qhov tob uas tshwm sim los ntawm P. aeruginosa yog 0.52 µm ntawm 7 hnub thiab 0.69 µm ntawm 14 hnub, raws li qhov nruab nrab qhov siab qhov tob ntawm 3 cov qauv (10 qhov siab tshaj qhov tob tau xaiv rau txhua tus qauv).Kev ua tiav ntawm 0.42 ± 0.12 µm thiab 0.52 ± 0.15 µm, ntsig txog (Table 5).Cov qhov tob qhov tseem ceeb no me me tab sis tseem ceeb.
(a) ua ntej raug, (b) 14 hnub nyob rau hauv ib puag ncig abiotic, thiab (c) 14 hnub hauv Pseudomonas aeruginosa broth.
Ntawm daim duab.Table 8 qhia txog XPS spectra ntawm ntau yam qauv saum npoo, thiab cov tshuaj muaj pes tsawg leeg tshuaj ntsuam xyuas rau txhua qhov saum npoo tau sau tseg hauv Table 6. Hauv Table 6, atomic feem pua ​​​​ntawm Fe thiab Cr nyob rau hauv lub xub ntiag ntawm P. aeruginosa (cov qauv A thiab B) tau qis dua li cov uas tsis yog tshuaj lom neeg tswj.(cov qauv C thiab D).Rau cov qauv P. aeruginosa, spectral nkhaus ntawm theem ntawm Cr 2p nucleus tau haum rau plaub lub ncov siab nrog kev sib khi zog (BE) ntawm 574.4, 576.6, 578.3 thiab 586.8 eV, uas tuaj yeem raug ntaus nqi rau Cr, Cr2O3,thiab Cr(OH)3, raws li (Fig. 9a thiab b).Rau cov qauv uas tsis yog-biological, lub spectrum ntawm lub ntsiab Cr 2p theem muaj ob lub ntsiab ncov rau Cr (573.80 eV rau BE) thiab Cr2O3 (575.90 eV rau BE) hauv daim duab.9c d ,ua.Qhov sib txawv tshaj plaws ntawm cov qauv abiotic thiab cov qauv P. aeruginosa yog qhov muaj Cr6+ thiab cov txheeb ze ntau dua ntawm Cr(OH)3 (BE 586.8 eV) nyob rau hauv biofilm.
Qhov dav XPS spectra ntawm qhov saum npoo ntawm cov qauv 2707 HDSS hauv ob qhov kev tshaj tawm yog 7 thiab 14 hnub, feem.
(a) 7 hnub raug P. aeruginosa, (b) 14 hnub raug rau P. aeruginosa, (c) 7 hnub nyob rau hauv ib puag ncig abiotic, thiab (d) 14 hnub nyob rau hauv ib puag ncig abiotic.
HDSS nthuav tawm qib siab ntawm corrosion kuj nyob rau hauv feem ntau ib puag ncig.Kim et al.2 tau tshaj tawm tias HDSS UNS S32707 tau txheeb xyuas tias yog DSS alloyed heev nrog PREN ntau dua 45. Tus nqi PREN ntawm cov qauv 2707 HDSS hauv txoj haujlwm no yog 49. Qhov no yog vim muaj cov ntsiab lus chromium siab thiab cov ntsiab lus siab ntawm molybdenum thiab npib tsib xee, uas muaj txiaj ntsig zoo hauv acidic ib puag ncig.thiab ib puag ncig nrog cov ntsiab lus chloride siab.Tsis tas li ntawd, kev sib xyaw ua ke zoo thiab tsis muaj qhov tsis zoo ntawm microstructure muaj txiaj ntsig zoo rau cov qauv kev ruaj ntseg thiab kev tiv thaiv corrosion.Txawm li cas los xij, txawm hais tias nws cov tshuaj tiv thaiv zoo heev, cov ntaub ntawv sim hauv cov haujlwm no qhia tias 2707 HDSS tsis muaj kev tiv thaiv tag nrho rau P. aeruginosa biofilm MICs.
Electrochemical cov txiaj ntsig tau pom tias tus nqi corrosion ntawm 2707 HDSS hauv P. aeruginosa broth tau nce ntau tom qab 14 hnub piv rau qhov chaw tsis muaj roj ntsha.Hauv daim duab 2a, qhov txo qis hauv Eocp tau pom ob qho tib si hauv nruab nrab abiotic thiab hauv P. aeruginosa broth thaum thawj 24 teev.Tom qab ntawd, lub biofilm tag nrho npog qhov chaw ntawm tus qauv, thiab Eocp ua tau ruaj khov36.Txawm li cas los xij, qib roj ntsha Eocp tau siab dua li qib tsis-biological Eocp.Muaj cov laj thawj ntseeg tias qhov sib txawv no cuam tshuam nrog kev tsim ntawm P. aeruginosa biofilms.Ntawm daim duab.2d nyob rau hauv lub xub ntiag ntawm P. aeruginosa, lub icorr 2707 HDSS tus nqi mus txog 0.627 μA cm-2, uas yog ib qho kev txiav txim ntawm magnitude siab tshaj qhov kev tswj ntawm abiotic (0.063 μA cm-2), uas yog raws li tus nqi Rct ntsuas los ntawm EIS.Nyob rau hauv thawj ob peb hnub, impedance qhov tseem ceeb nyob rau hauv lub P. aeruginosa broth tau nce vim qhov txuas ntawm P. aeruginosa hlwb thiab tsim cov biofilms.Txawm li cas los xij, thaum lub biofilm npog tag nrho cov qauv saum npoo, qhov impedance txo.Cov txheej tiv thaiv yog tawm tsam feem ntau vim yog tsim ntawm biofilms thiab biofilm metabolites.Yog li ntawd, qhov kev tiv thaiv corrosion tau txo qis thaum lub sijhawm thiab qhov txuas ntawm P. aeruginosa ua rau muaj kev cuam tshuam hauv zos.Cov kev xav hauv ib puag ncig abiotic txawv.Qhov kev tiv thaiv corrosion ntawm cov kev tswj tsis-biological tau ntau dua li tus nqi sib thooj ntawm cov qauv raug rau P. aeruginosa broth.Tsis tas li ntawd, rau abiotic accessions, Rct 2707 HDSS tus nqi mus txog 489 kΩ cm2 nyob rau hnub 14, uas yog 15 npaug siab dua tus nqi Rct (32 kΩ cm2) nyob rau hauv lub xub ntiag ntawm P. aeruginosa.Yog li, 2707 HDSS muaj kev tiv thaiv zoo heev hauv qhov chaw tsis muaj menyuam, tab sis tsis tiv taus MICs los ntawm P. aeruginosa biofilms.
Cov txiaj ntsig no tseem tuaj yeem pom los ntawm cov kab nkhaus polarization hauv Fig.2b ib.Anodic branching tau txuam nrog Pseudomonas aeruginosa biofilm tsim thiab hlau oxidation cov tshuaj tiv thaiv.Hauv qhov no, cov tshuaj tiv thaiv cathodic yog qhov txo qis ntawm oxygen.Lub xub ntiag ntawm P. aeruginosa ho nce qhov corrosion tam sim no ceev, hais txog qhov kev txiav txim ntawm qhov loj dua li kev tswj hwm abiotic.Qhov no qhia tau hais tias P. aeruginosa biofilm txhim kho qhov chaw corrosion ntawm 2707 HDSS.Yuan et al.29 pom tias qhov corrosion tam sim no ceev ntawm Cu-Ni 70/30 alloy nce nyob rau hauv qhov kev txiav txim ntawm P. aeruginosa biofilm.Qhov no tej zaum yuav yog vim biocatalysis ntawm oxygen txo los ntawm Pseudomonas aeruginosa biofilms.Qhov kev soj ntsuam no kuj tseem tuaj yeem piav qhia MIC 2707 HDSS hauv txoj haujlwm no.Tej zaum kuj yuav muaj cov pa oxygen tsawg dua hauv aerobic biofilms.Yog li, qhov tsis kam rov ua dua cov hlau nto nrog cov pa oxygen tuaj yeem yog qhov ua rau MIC hauv txoj haujlwm no.
Dickinson thiab al.38 qhia tias tus nqi ntawm cov tshuaj lom neeg thiab cov tshuaj electrochemical tuaj yeem cuam tshuam ncaj qha los ntawm kev ua haujlwm metabolic ntawm cov kab mob sessile ntawm tus qauv saum npoo thiab qhov xwm txheej ntawm cov khoom siv corrosion.Raws li pom nyob rau hauv daim duab 5 thiab Table 5, cov cell thiab biofilm thickness txo qis tom qab 14 hnub.Qhov no tuaj yeem piav qhia tau zoo los ntawm qhov tseeb tias tom qab 14 hnub, feem ntau ntawm cov sessile hlwb nyob rau saum npoo ntawm 2707 HDSS tuag vim yog cov khoom noj tsis txaus hauv 2216E nruab nrab lossis tso tawm cov tshuaj lom hlau ions los ntawm 2707 HDSS matrix.Qhov no yog ib qho kev txwv ntawm kev sim batch.
Hauv kev ua haujlwm no, P. aeruginosa biofilm tau pab txhawb rau lub zos depletion ntawm Cr thiab Fe nyob rau hauv lub biofilm nyob rau saum npoo ntawm 2707 HDSS (Fig. 6).Table 6 qhia txog qhov txo qis hauv Fe thiab Cr hauv cov qauv D piv rau cov qauv C, qhia tias cov yaj Fe thiab Cr tshwm sim los ntawm P. aeruginosa biofilm txuas ntxiv rau thawj 7 hnub.2216E ib puag ncig yog siv los simulate ib puag ncig marine.Nws muaj 17700 ppm Cl-, uas yog piv rau nws cov ntsiab lus hauv dej hiav txwv ntuj.Lub xub ntiag ntawm 17700 ppm Cl- yog qhov laj thawj tseem ceeb rau kev txo qis hauv Cr hauv 7- thiab 14-hnub cov qauv abiotic tshuaj ntsuam xyuas los ntawm XPS.Piv nrog rau cov qauv P. aeruginosa, qhov kev sib cais ntawm Cr hauv cov qauv abiotic yog tsawg dua vim qhov muaj zog tsis kam ntawm 2707 HDSS rau chlorine nyob rau hauv cov kab mob abiotic.Ntawm daim duab.9 qhia pom muaj Cr6+ hauv zaj duab xis passivating.Tej zaum nws yuav koom nrog kev tshem tawm cov chromium los ntawm steel nto los ntawm P. aeruginosa biofilms, raws li tau hais los ntawm Chen thiab Clayton.
Vim cov kab mob loj hlob, pH qhov nruab nrab ntawm qhov nruab nrab ua ntej thiab tom qab cog yog 7.4 thiab 8.2, raws li.Yog li, hauv qab P. aeruginosa biofilm, organic acid corrosion tsis zoo li yuav pab txhawb rau txoj haujlwm no vim muaj pH siab nyob rau hauv qhov nruab nrab.Cov pH ntawm qhov nruab nrab tsis-biological tswj tsis tau hloov pauv loj heev (los ntawm thawj 7.4 mus rau qhov kawg 7.5) thaum lub sijhawm kuaj 14 hnub.Qhov nce ntawm pH nyob rau hauv cov noob nruab nrab tom qab incubation yog vim lub metabolic kev ua ntawm P. aeruginosa thiab tau pom tias muaj ib tug tib yam nyhuv ntawm pH nyob rau hauv tsis muaj cov tshuaj ntsuam strips.
Raws li pom nyob rau hauv daim duab 7, qhov siab tshaj plaws qhov tob tshwm sim los ntawm P. aeruginosa biofilm yog 0.69 µm, uas yog ntau dua li qhov nruab nrab abiotic (0.02 µm).Qhov no yog ua raws li cov ntaub ntawv electrochemical tau piav qhia saum toj no.Lub qhov tob ntawm 0.69 µm yog ntau tshaj kaum npaug me dua li 9.5 µm tus nqi qhia rau 2205 DSS nyob rau hauv tib lub sijhawm.Cov ntaub ntawv no qhia tau hais tias 2707 HDSS nthuav tawm zoo dua rau MICs dua 2205 DSS.Qhov no yuav tsum tsis txhob xav tsis thoob vim tias 2707 HDSS muaj ntau dua Cr qib uas muab ntev dua passivation, nyuaj rau depassivate P. aeruginosa, thiab vim tias nws cov theem sib npaug tsis muaj teeb meem nag lossis daus ua rau pitting.
Hauv kev xaus, MIC pits tau pom nyob rau saum npoo ntawm 2707 HDSS hauv P. aeruginosa broth piv rau qhov tsis tseem ceeb hauv thaj chaw abiotic.Qhov kev ua haujlwm no qhia tau hais tias 2707 HDSS muaj kev tiv thaiv zoo rau MIC dua li 2205 DSS, tab sis nws tsis muaj zog tiv thaiv MIC vim P. aeruginosa biofilm.Cov txiaj ntsig no pab xaiv cov hlau tsis zoo thiab lub neej expectancy rau marine ib puag ncig.
Daim coupon rau 2707 HDSS muab los ntawm Northeastern University (NEU) Lub Tsev Kawm Ntawv ntawm Metallurgy hauv Shenyang, Suav.Lub hauv paus muaj pes tsawg leeg ntawm 2707 HDSS yog qhia hauv Table 1, uas tau soj ntsuam los ntawm NEU Materials Analysis thiab Test Department.Tag nrho cov qauv raug kho rau cov kua dej ntawm 1180 ° C rau 1 teev.Ua ntej kev kuaj corrosion, lub npib zoo li 2707 HDSS nrog rau sab saum toj qhib qhov chaw ntawm 1 cm2 tau polished rau 2000 grit nrog silicon carbide sandpaper thiab tom qab ntawd polished nrog 0.05 µm Al2O3 hmoov slurry.Sab thiab hauv qab yog tiv thaiv nrog inert xim.Tom qab ziab, cov qauv raug ntxuav nrog dej tsis muaj deionized thiab sterilized nrog 75% (v / v) ethanol rau 0.5 h.Tom qab ntawd lawv tau muab cua qhuav nyob rau hauv ultraviolet (UV) lub teeb rau 0.5 teev ua ntej siv.
Marine Pseudomonas aeruginosa strain MCCC 1A00099 tau yuav los ntawm Xiamen Marine Culture Collection Center (MCCC), Tuam Tshoj.Pseudomonas aeruginosa tau loj hlob nyob rau hauv aerobic mob ntawm 37 ° C. nyob rau hauv 250 ml flasks thiab 500 ml iav electrochemical hlwb siv Marine 2216E kua nruab nrab (Qingdao Hope Biotechnology Co., Ltd., Qingdao, Tuam Tshoj).Nruab nrab muaj (g/l): 19.45 NaCl, 5.98 MgCl2, 3.24 Na2SO4, 1.8 CaCl2, 0.55 KCl, 0.16 Na2CO3, 0.08 KBr, 0.034 SrCl2, 0.08 SrBr30020, H. 16 6NH26NH3, 3.0016 NH3 5.0 peptone, 1.0 poov xab extract thiab 0.1 hlau citrate.Autoclave ntawm 121 ° C rau 20 feeb ua ntej inoculation.Suav cov sessile thiab planktonic hlwb nrog lub hemocytometer nyob rau hauv lub teeb lub teeb microscope ntawm 400x magnification.Thawj qhov concentration ntawm planktonic Pseudomonas aeruginosa tam sim ntawd tom qab inoculation yog kwv yees li 106 hlwb / ml.
Electrochemical kev ntsuam xyuas tau ua nyob rau hauv ib tug classic peb-electrode iav cell nrog ib tug nruab nrab ntim ntawm 500 ml.Daim ntawv platinum thiab saturated calomel electrode (SAE) tau txuas nrog lub reactor los ntawm Luggin capillaries uas muaj ntsev txuas hniav, uas ua hauj lwm raws li txee thiab siv electrodes, feem.Rau kev tsim cov khoom siv hluav taws xob ua haujlwm, cov roj hmab tooj liab tau txuas rau txhua tus qauv thiab npog nrog epoxy resin, tawm hauv thaj tsam li 1 cm2 ntawm qhov tsis muaj kev tiv thaiv rau cov electrode ua haujlwm ntawm ib sab.Thaum lub sij hawm ntsuas electrochemical, cov qauv tau muab tso rau hauv qhov nruab nrab 2216E thiab khaws cia ntawm qhov kub thiab txias (37 ° C) hauv dej da dej.OCP, LPR, EIS thiab cov ntaub ntawv muaj peev xwm dynamic polarization tau ntsuas siv Autolab potentiostat (Reference 600TM, Gamry Instruments, Inc., USA).LPR cov kev ntsuam xyuas tau sau tseg ntawm qhov ntsuas ntsuas ntawm 0.125 mV s-1 nyob rau hauv thaj tsam ntawm -5 txog 5 mV nrog Eocp thiab tus lej ntsuas ntawm 1 Hz.EIS tau ua nrog sine nthwv dej ntawm qhov ntau zaus ntawm 0.01 txog 10,000 Hz siv qhov siv hluav taws xob ntawm 5 mV ntawm lub xeev ruaj khov Eocp.Ua ntej lub peev xwm cheb, cov electrodes tau nyob rau hauv hom tsis ua haujlwm kom txog rau thaum tus nqi ruaj khov ntawm qhov muaj peev xwm corrosion dawb.Lub polarization nkhaus tau ntsuas los ntawm -0.2 txog 1.5 V raws li kev ua haujlwm ntawm Eocp ntawm tus nqi scan ntawm 0.166 mV / s.Txhua qhov kev sim tau rov ua dua 3 zaug nrog thiab tsis muaj P. aeruginosa.
Cov qauv rau kev tsom xam metallographic tau mechanically polished nrog ntub 2000 grit SiC ntawv thiab tom qab ntawd ntxiv polished nrog 0.05 µm Al2O3 hmoov raug tshem tawm rau kev soj ntsuam kho qhov muag.Metallographic tsom xam tau ua los ntawm kev siv lub tshuab ntsuas qhov muag.Cov qauv tau etched nrog 10 wt% daws ntawm potassium hydroxide 43.
Tom qab incubation, cov qauv raug ntxuav 3 zaug nrog phosphate buffered saline (PBS) (pH 7.4 ± 0.2) thiab tom qab ntawd kho nrog 2.5% (v/v) glutaraldehyde rau 10 teev los kho biofilms.Tom qab ntawd nws tau dehydrated nrog batched ethanol (50%, 60%, 70%, 80%, 90%, 95% thiab 100% los ntawm ntim) ua ntej cua ziab.Thaum kawg, cov yeeb yaj kiab kub tau muab tso rau saum npoo ntawm cov qauv los muab kev coj ua rau SEM kev soj ntsuam.SEM cov duab tau tsom mus rau cov chaw uas muaj cov kab mob P. aeruginosa ntau tshaj plaws nyob rau saum npoo ntawm txhua tus qauv.Ua ib qho kev ntsuam xyuas EDS kom pom cov tshuaj lom neeg.Zeiss confocal laser scanning microscope (CLSM) (LSM 710, Zeiss, Lub teb chaws Yelemees) tau siv los ntsuas lub qhov tob.Txhawm rau soj ntsuam cov pits corrosion nyob rau hauv biofilm, cov qauv kuaj tau raug ntxuav ua ntej raws li Suav Teb Chaws Standard (CNS) GB / T4334.4-2000 kom tshem tawm cov khoom corrosion thiab biofilm los ntawm qhov chaw ntawm cov qauv kuaj.
X-ray photoelectron spectroscopy (XPS, ESCALAB250 nto tsom xam qhov system, Thermo VG, USA) kev tsom xam tau ua los ntawm kev siv lub monochromatic X-ray qhov chaw (Aluminium Kα kab nrog lub zog ntawm 1500 eV thiab lub zog ntawm 150 W) nyob rau hauv ntau yam kev sib khi energies 0.Cov kev daws teeb meem siab tau sau tseg siv lub zog sib kis ntawm 50 eV thiab ib kauj ruam ntawm 0.2 eV.
Cov qauv incubated raug tshem tawm thiab ntxuav maj mam nrog PBS (pH 7.4 ± 0.2) rau 15 s45.Txhawm rau soj ntsuam cov kab mob viability ntawm biofilms ntawm cov qauv, biofilms tau stained siv LIVE/DEAD BacLight Bacterial Viability Kit (Invitrogen, Eugene, OR, USA).Cov khoom siv muaj ob fluorescent dyes: SYTO-9 ntsuab fluorescent dye thiab propidium iodide (PI) liab fluorescent dye.Hauv CLSM, fluorescent ntsuab thiab liab dots sawv cev rau cov cell nyob thiab tuag, raws li.Rau staining, 1 ml ntawm cov sib tov uas muaj 3 μl ntawm SYTO-9 thiab 3 μl ntawm PI tov yog incubated rau 20 feeb ntawm chav tsev kub (23 ° C) nyob rau hauv qhov tsaus ntuj nti.Tom qab ntawd, cov qauv stained raug tshuaj xyuas ntawm ob lub wavelengths (488 nm rau cov hlwb nyob thiab 559 nm rau cov hlwb tuag) siv Nikon CLSM apparatus (C2 Plus, Nikon, Nyiv).Biofilm thickness tau ntsuas hauv 3D scanning hom.
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