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Kev xeb ntawm cov kab mob me me (MIC) yog ib qho teeb meem loj heev hauv ntau lub lag luam vim nws tuaj yeem ua rau muaj kev poob nyiaj txiag loj heev. 2707 super duplex stainless hlau (2707 HDSS) tau siv rau hauv cov chaw ib puag ncig marine vim nws cov tshuaj tiv thaiv zoo heev. Txawm li cas los xij, nws qhov kev tiv thaiv rau MIC tsis tau pom tseeb los ntawm kev sim. Hauv kev tshawb fawb no, tus cwj pwm MIC ntawm 2707 HDSS tshwm sim los ntawm cov kab mob marine aerobic Pseudomonas aeruginosa tau tshawb xyuas. Kev tshuaj xyuas electrochemical qhia tau hais tias nyob rau hauv qhov muaj Pseudomonas aeruginosa biofilm hauv 2216E nruab nrab, muaj kev hloov pauv zoo hauv kev xeb thiab kev nce ntxiv ntawm qhov ceev tam sim no xeb. X-ray photoelectron spectroscopy (XPS) kev tshuaj xyuas qhia tau tias qhov txo qis hauv Cr cov ntsiab lus ntawm qhov chaw ntawm cov qauv hauv qab biofilm. Kev tshuaj xyuas duab ntawm cov qhov av qhia tau hais tias P. aeruginosa biofilm tsim qhov tob tshaj plaws ntawm 0.69 μm thaum 14 hnub ntawm kev sib xyaw. Txawm hais tias qhov no me me, nws qhia tau hais tias 2707 HDSS tsis muaj zog tag nrho. rau MIC ntawm P. aeruginosa biofilms.
Cov hlau tsis xeb duplex (DSS) siv dav hauv ntau yam lag luam rau lawv qhov kev sib xyaw ua ke zoo tshaj plaws ntawm cov khoom siv kho tshuab zoo heev thiab kev tiv thaiv corrosion1,2. Txawm li cas los xij, qhov chaw pitting tseem tshwm sim thiab nws cuam tshuam rau kev ncaj ncees ntawm cov hlau no3,4. DSS tsis tiv taus microbial corrosion (MIC)5,6. Txawm hais tias muaj ntau yam kev siv ntawm DSS, tseem muaj ib puag ncig uas qhov kev tiv thaiv corrosion ntawm DSS tsis txaus rau kev siv mus sij hawm ntev. Qhov no txhais tau tias cov ntaub ntawv kim dua nrog kev tiv thaiv corrosion siab dua yog qhov xav tau. Jeon et al7 pom tias txawm tias super duplex stainless steels (SDSS) muaj qee qhov kev txwv hauv kev tiv thaiv corrosion. Yog li ntawd, super duplex stainless steels (HDSS) nrog kev tiv thaiv corrosion siab dua yog qhov xav tau hauv qee daim ntawv thov. Qhov no ua rau kev txhim kho ntawm cov hlau alloyed siab.
Qhov kev tiv thaiv corrosion ntawm DSS nyob ntawm qhov sib piv ntawm alpha thiab gamma theem thiab Cr, Mo thiab W depleted cheeb tsam 8, 9, 10 nyob ib sab ntawm theem thib 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) Pitting Resistance Equivalent Number (PREN), txiav txim siab los ntawm wt.% Cr + 3.3 (wt.% Mo + 0.5 wt% W) + 16 wt% N12. Nws qhov kev tiv thaiv corrosion zoo heev nyob ntawm qhov sib npaug uas muaj kwv yees li 50% ferrite (α) thiab 50% austenite (γ) theem, HDSS muaj cov khoom siv kho tshuab zoo dua thiab kev tiv thaiv siab dua li DSS13 ib txwm muaj. Cov khoom siv corrosion chloride. Qhov kev tiv thaiv corrosion zoo dua nthuav dav kev siv HDSS hauv cov chaw muaj corrosive chloride ntau dua, xws li cov chaw marine.
MICs yog ib qho teeb meem loj hauv ntau lub lag luam xws li roj thiab roj av thiab cov chaw siv dej14.MIC suav txog 20% ​​ntawm tag nrho cov kev puas tsuaj los ntawm kev xeb15.MIC yog kev xeb bioelectrochemical uas tuaj yeem pom hauv ntau qhov chaw ib puag ncig. Cov biofilms uas tsim rau ntawm cov hlau hloov pauv cov xwm txheej electrochemical, yog li cuam tshuam rau cov txheej txheem xeb. Nws ntseeg tau tias kev xeb MIC yog tshwm sim los ntawm biofilms. Cov kab mob electronic corrode cov hlau kom tau txais lub zog txhawb nqa kom muaj sia nyob17. Cov kev tshawb fawb MIC tsis ntev los no tau qhia tias EET (extracellular electron transfer) yog qhov txwv tus nqi hauv MIC uas tshwm sim los ntawm cov kab mob electrogenic.Zhang et al. 18 tau qhia tias cov neeg sib tham electron ua kom nrawm hloov pauv electron ntawm Desulfovibrio sessificans hlwb thiab 304 stainless hlau, ua rau MIC tawm tsam hnyav dua.Enning et al. 19 thiab Venzlaff et al. 20 tau qhia tias cov kab mob corrosive sulfate-reducing bacteria (SRB) biofilms tuaj yeem nqus cov electrons ncaj qha los ntawm cov hlau substrates, ua rau muaj kev xeb pitting hnyav.
DSS paub tias muaj kev phom sij rau MIC nyob rau hauv cov chaw muaj SRB, cov kab mob txo cov hlau (IRB), thiab lwm yam. 21. Cov kab mob no ua rau muaj qhov chaw nyob ntawm DSS qhov chaw nyob hauv qab biofilms22,23. Tsis zoo li DSS, MIC ntawm HDSS24 tsis paub zoo.
Pseudomonas aeruginosa yog ib hom kab mob gram-negative uas muaj cov duab zoo li tus pas nrig uas muaj ntau yam nyob hauv xwm25. Pseudomonas aeruginosa kuj yog ib pawg kab mob loj hauv dej hiav txwv, ua rau MIC ua rau hlau. Pseudomonas muaj feem cuam tshuam nrog cov txheej txheem xeb thiab raug lees paub tias yog tus thawj coj hauv kev tsim cov biofilm. Mahat et al. 28 thiab Yuan et al. 29 tau qhia tias Pseudomonas aeruginosa muaj feem ua rau kom cov hlau tsis muaj zog thiab cov hlau sib xyaw ua rau cov hlau tsis xeb ntau ntxiv hauv cov dej.
Lub hom phiaj tseem ceeb ntawm txoj haujlwm no yog los tshawb nrhiav cov khoom MIC ntawm 2707 HDSS uas tshwm sim los ntawm cov kab mob hauv dej hiav txwv Pseudomonas aeruginosa siv cov txheej txheem electrochemical, cov txheej txheem analytical nto thiab kev tshuaj xyuas cov khoom corrosion. Kev tshawb fawb electrochemical suav nrog Open Circuit Potential (OCP), Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS), thiab Potential Dynamic Polarization tau ua los kawm txog MIC tus cwj pwm ntawm 2707 HDSS. Kev tshuaj xyuas lub zog dispersive spectrometer (EDS) tau ua los nrhiav cov tshuaj lom neeg ntawm qhov chaw corroded. Tsis tas li ntawd, X-ray photoelectron spectroscopy (XPS) kev tshuaj xyuas 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 qhov av tau ntsuas nyob rau hauv lub confocal laser scanning microscope (CLSM).
Rooj 1 teev cov tshuaj lom neeg sib xyaw ntawm 2707 HDSS. Rooj 2 qhia tau tias 2707 HDSS muaj cov khoom siv kho tshuab zoo heev nrog lub zog tso zis ntawm 650 MPa. Daim duab 1 qhia txog qhov microstructure optical ntawm cov tshuaj kho cua sov 2707 HDSS. Cov kab ntev ntawm austenite thiab ferrite theem tsis muaj theem thib ob tuaj yeem pom hauv microstructure uas muaj li 50% austenite thiab 50% ferrite theem.
Daim Duab 2a qhia txog qhov qhib lub voj voog muaj peev xwm (Eocp) piv rau lub sijhawm raug cov ntaub ntawv rau 2707 HDSS hauv abiotic 2216E nruab nrab thiab P. aeruginosa kua zaub rau 14 hnub ntawm 37 ° C. Nws qhia tau hais tias qhov kev hloov pauv loj tshaj plaws thiab tseem ceeb hauv Eocp tshwm sim hauv thawj 24 teev. Cov nqi Eocp hauv ob qho xwm txheej tau nce siab tshaj plaws ntawm -145 mV (vs. SCE) nyob ib puag ncig 16 teev thiab tom qab ntawd poob qis, ncav cuag -477 mV (vs. SCE) thiab -236 mV (vs. SCE) rau cov qauv abiotic thiab P, feem). Cov daim coupon Pseudomonas aeruginosa, raws li. Tom qab 24 teev, tus nqi Eocp ntawm 2707 HDSS rau P. aeruginosa ruaj khov ntawm -228 mV (vs. SCE), thaum tus nqi sib xws rau cov qauv tsis yog biological yog kwv yees li -442 mV (vs. SCE). Eocp nyob rau hauv lub xub ntiag ntawm P. aeruginosa yog qhov qis heev.
Kev kuaj hluav taws xob ntawm 2707 HDSS cov qauv hauv abiotic medium thiab Pseudomonas aeruginosa broth ntawm 37 ° C:
(a) Eocp ua haujlwm ntawm lub sijhawm raug, (b) cov kab polarization ntawm hnub 14, (c) Rp ua haujlwm ntawm lub sijhawm raug thiab (d) icorr ua haujlwm ntawm lub sijhawm raug.
Rooj 3 teev cov nqi electrochemical corrosion parameter ntawm 2707 HDSS qauv raug rau abiotic medium thiab Pseudomonas aeruginosa inoculated medium rau 14 hnub. Cov tangents ntawm cov anodic thiab cathodic curves tau extrapolated kom tuaj txog ntawm qhov kev sib tshuam yielding corrosion tam sim no density (icorr), corrosion potential (Ecorr) thiab Tafel slopes (βα thiab βc) raws li cov qauv txheem 30,31.
Raws li pom hauv Daim Duab 2b, qhov kev hloov pauv ntawm P. aeruginosa nkhaus ua rau muaj kev nce ntxiv hauv Ecorr piv rau qhov nkhaus abiotic. Tus nqi icorr, uas yog proportional rau qhov corrosion rate, nce mus txog 0.328 μA cm-2 hauv Pseudomonas aeruginosa qauv, plaub npaug ntawm cov qauv tsis yog biological (0.087 μA cm-2).
LPR yog ib txoj kev siv hluav taws xob uas tsis ua rau puas tsuaj rau kev tshuaj xyuas xeb sai. Nws kuj tau siv los kawm MIC32. Daim duab 2c qhia txog qhov tsis kam polarization (Rp) ua lub luag haujlwm ntawm lub sijhawm raug. Tus nqi Rp siab dua txhais tau tias muaj xeb tsawg dua. Hauv 24 teev thawj zaug, Rp ntawm 2707 HDSS tau mus txog tus nqi siab tshaj plaws ntawm 1955 kΩ cm2 rau cov qauv abiotic thiab 1429 kΩ cm2 rau cov qauv Pseudomonas aeruginosa. Daim duab 2c kuj qhia tau tias tus nqi Rp tau txo qis sai tom qab ib hnub thiab tom qab ntawd tseem tsis hloov pauv rau 13 hnub tom ntej. Tus nqi Rp ntawm cov qauv Pseudomonas aeruginosa yog li 40 kΩ cm2, uas qis dua tus nqi 450 kΩ cm2 ntawm cov qauv tsis yog biological.
Tus nqi icorr yog proportional rau qhov sib npaug ntawm corrosion. Nws tus nqi tuaj yeem suav los ntawm cov kab zauv Stern-Geary hauv qab no,
Ua raws li Zou et al. 33, tus nqi ib txwm ntawm Tafel slope B hauv txoj haujlwm no tau xav tias yog 26 mV / dec. Daim duab 2d qhia tau hais tias icorr ntawm cov qauv tsis yog biological 2707 tseem ruaj khov, thaum cov qauv P. aeruginosa hloov pauv ntau tom qab 24 teev thawj zaug. Cov nqi icorr ntawm cov qauv P. aeruginosa yog qhov kev txiav txim siab ntawm qhov loj dua li cov kev tswj tsis yog biological. Qhov sib txawv no yog sib xws nrog cov txiaj ntsig polarization tsis kam.
EIS yog lwm txoj kev tsis puas tsuaj uas siv los piav qhia txog cov tshuaj electrochemical ntawm cov interfaces corroded. Impedance spectra thiab cov nqi capacitance xam ntawm cov qauv uas raug rau abiotic media thiab Pseudomonas aeruginosa kua, Rb tsis kam ntawm passive zaj duab xis / biofilm tsim rau ntawm qhov chaw ntawm cov qauv, Rct them hloov tsis kam, Cdl hluav taws xob ob txheej capacitance (EDL) thiab QCPE Constant Phase Element (CPE) cov kev cai. Cov kev cai no tau raug soj ntsuam ntxiv los ntawm kev haum cov ntaub ntawv siv cov qauv sib npaug (EEC).
Daim Duab 3 qhia txog cov qauv Nyquist (a thiab b) thiab Bode (a' thiab b') ntawm 2707 HDSS cov qauv hauv abiotic medium thiab P. aeruginosa broth rau lub sijhawm sib txawv. Lub cheeb tsam ntawm Nyquist ring txo qis thaum muaj Pseudomonas aeruginosa. Daim duab Bode (Daim Duab 3b') qhia txog kev nce ntxiv ntawm qhov loj ntawm tag nrho impedance. Cov ntaub ntawv ntawm lub sijhawm so tsis tu ncua tuaj yeem muab los ntawm theem maxima. Daim Duab 4 qhia txog monolayer (a) thiab bilayer (b) raws li cov qauv lub cev thiab lawv cov EECs sib xws. CPE tau qhia rau hauv EEC qauv. Nws qhov kev nkag mus thiab impedance tau qhia raws li hauv qab no:
Ob lub qauv lub cev thiab cov voj voog sib npaug sib xws rau kev haum rau qhov impedance spectrum ntawm 2707 HDSS qauv:
qhov twg Y0 yog qhov loj ntawm CPE, j yog tus lej xav lossis (-1)1/2, ω yog lub zaus kaum sab xis, thiab n yog CPE lub zog ntsuas tsawg dua unity35. Qhov rov qab ntawm qhov tsis kam hloov pauv (piv txwv li 1/Rct) sib raug rau qhov nrawm ntawm kev xeb. Rct me dua txhais tau tias qhov nrawm ntawm kev xeb sai dua27. Tom qab 14 hnub ntawm kev sib xyaw, Rct ntawm cov qauv Pseudomonas aeruginosa tau txog 32 kΩ cm2, me dua li 489 kΩ cm2 ntawm cov qauv tsis yog biological (Rooj 4).
Cov duab CLSM thiab cov duab SEM hauv Daim Duab 5 qhia meej meej tias qhov biofilm npog ntawm qhov chaw ntawm 2707 HDSS qauv tom qab 7 hnub yog ntom. Txawm li cas los xij, tom qab 14 hnub, qhov biofilm npog tsis tshua muaj thiab qee cov hlwb tuag tshwm sim. Rooj 5 qhia qhov tuab ntawm biofilm ntawm 2707 HDSS qauv tom qab raug P. aeruginosa rau 7 thiab 14 hnub. Qhov tuab ntawm biofilm siab tshaj plaws tau hloov pauv ntawm 23.4 μm tom qab 7 hnub mus rau 18.9 μm tom qab 14 hnub. Qhov nruab nrab ntawm biofilm tuab kuj lees paub qhov sib txawv no. Nws txo qis los ntawm 22.2 ± 0.7 μm tom qab 7 hnub mus rau 17.8 ± 1.0 μm tom qab 14 hnub.
(a) duab 3-D CLSM tom qab 7 hnub, (b) duab 3-D CLSM tom qab 14 hnub, (c) duab SEM tom qab 7 hnub thiab (d) duab SEM tom qab 14 hnub.
EDS tau qhia txog cov tshuaj lom neeg hauv cov biofilms thiab cov khoom xeb ntawm cov qauv uas raug rau P. aeruginosa rau 14 hnub. Daim duab 6 qhia tau hais tias cov ntsiab lus ntawm C, N, O, thiab P hauv biofilms thiab cov khoom xeb yog siab dua li ntawm cov hlau liab qab, vim tias cov ntsiab lus no cuam tshuam nrog biofilms thiab lawv cov metabolites. Cov kab mob me me tsuas yog xav tau cov chromium thiab hlau me ntsis xwb. Cov theem siab ntawm Cr thiab Fe hauv biofilm thiab cov khoom xeb ntawm qhov chaw ntawm cov qauv qhia tau hais tias cov hlau matrix tau poob cov ntsiab lus vim yog xeb.
Tom qab 14 hnub, pom muaj cov qhov me me uas muaj thiab tsis muaj P. aeruginosa nyob rau hauv 2216E nruab nrab. Ua ntej kev sib xyaw, qhov chaw ntawm cov qauv tau du thiab tsis muaj qhov tsis zoo (Daim duab 7a). Tom qab kev sib xyaw thiab tshem tawm cov biofilm thiab cov khoom xeb, cov qhov tob tshaj plaws ntawm qhov chaw ntawm cov qauv tau kuaj xyuas hauv qab CLSM, raws li pom hauv Daim Duab 7b thiab c. Tsis muaj cov qhov me me pom tseeb ntawm qhov chaw ntawm cov qauv tswj tsis yog biological (qhov tob tshaj plaws ntawm qhov tob 0.02 μm). Qhov tob tshaj plaws ntawm qhov tob uas tshwm sim los ntawm Pseudomonas aeruginosa yog 0.52 μm tom qab 7 hnub thiab 0.69 μm tom qab 14 hnub, raws li qhov nruab nrab qhov tob tshaj plaws ntawm 3 cov qauv (10 qhov tob tshaj plaws ntawm qhov tob tau xaiv rau txhua tus qauv) tau txog 0.42 ± 0.12 μm thiab 0.52 ± 0.15 μm, feem (Rooj 5). Cov nqi tob ntawm qhov tob no me me tab sis tseem ceeb.
(a) Ua ntej raug tus kab mob, (b) 14 hnub nyob rau hauv abiotic medium thiab (c) 14 hnub nyob rau hauv Pseudomonas aeruginosa kua zaub.
Daim Duab 8 qhia txog XPS spectra ntawm cov qauv sib txawv, thiab cov tshuaj lom neeg sib xyaw ua ke rau txhua qhov chaw tau muab tso ua ke hauv Rooj 6. Hauv Rooj 6, feem pua ​​​​​​ntawm Fe thiab Cr nyob rau hauv qhov muaj P. aeruginosa (cov qauv A thiab B) qis dua li cov ntawm cov qauv tswj tsis yog biological (cov qauv C thiab D). Rau cov qauv P. aeruginosa, Cr 2p core-level spectral curve tau haum rau plaub lub ncov nrog cov nqi zog khi (BE) ntawm 574.4, 576.6, 578.3 thiab 586.8 eV, uas tuaj yeem raug suav tias yog Cr, Cr2O3, CrO3 thiab Cr (OH) 3, feem (Daim Duab 9a thiab b). Rau cov qauv tsis yog biological, Cr 2p core-level spectrum muaj ob lub ncov tseem ceeb rau Cr (573.80 eV rau BE) thiab Cr2O3 (575.90 eV rau BE) nyob rau hauv daim duab 9c thiab d, raws li. Qhov sib txawv tshaj plaws ntawm cov qauv abiotic thiab P. aeruginosa yog qhov muaj Cr6 + thiab feem pua ​​​​​​ntawm Cr (OH) 3 (BE ntawm 586.8 eV) hauv qab biofilm.
Cov spectra XPS dav dav ntawm qhov chaw ntawm 2707 HDSS qauv hauv ob qho xov xwm yog 7 hnub thiab 14 hnub, raws li.
(a) 7 hnub ntawm kev raug rau P. aeruginosa, (b) 14 hnub ntawm kev raug rau P. aeruginosa, (c) 7 hnub nyob rau hauv abiotic medium thiab (d) 14 hnub nyob rau hauv abiotic medium.
HDSS qhia txog qib siab ntawm kev tiv thaiv corrosion hauv feem ntau ib puag ncig. Kim et al. 2 tau tshaj tawm tias UNS S32707 HDSS tau txhais tias yog DSS uas muaj cov khoom sib xyaw ua ke nrog PREN ntau dua 45. Tus nqi PREN ntawm 2707 HDSS qauv hauv txoj haujlwm no yog 49. Qhov no yog vim nws cov ntsiab lus chromium siab thiab cov molybdenum thiab Ni siab, uas muaj txiaj ntsig zoo hauv cov chaw acidic thiab chloride siab. Tsis tas li ntawd, cov khoom sib npaug zoo thiab cov qauv tsis muaj qhov tsis zoo yog qhov muaj txiaj ntsig zoo rau kev ruaj khov ntawm cov qauv thiab kev tiv thaiv corrosion. Txawm li cas los xij, txawm tias nws cov tshuaj tiv thaiv zoo heev, cov ntaub ntawv sim hauv txoj haujlwm no qhia tias 2707 HDSS tsis tiv thaiv tag nrho rau MIC ntawm P. aeruginosa biofilms.
Cov txiaj ntsig electrochemical qhia tau hais tias qhov corrosion ntawm 2707 HDSS hauv P. aeruginosa broth tau nce ntxiv tom qab 14 hnub piv rau cov khoom tsis yog biological. Hauv Daim Duab 2a, qhov kev txo qis hauv Eocp tau pom hauv ob qho tib si abiotic medium thiab P. aeruginosa broth thaum 24 teev thawj zaug. Tom qab ntawd, cov biofilm tau ua tiav npog qhov chaw ntawm cov qauv thiab Eocp dhau los ua qhov ruaj khov 36. Txawm li cas los xij, qib ntawm biological Eocp siab dua li ntawm cov khoom tsis yog biological Eocp. Muaj laj thawj ntseeg tias qhov sib txawv no yog vim P. aeruginosa biofilm tsim. Hauv Daim Duab 2d, nyob rau hauv qhov muaj P. aeruginosa, tus nqi icorr ntawm 2707 HDSS tau mus txog 0.627 μA cm-2, uas yog qhov kev txiav txim siab ntawm qhov loj dua li ntawm abiotic tswj (0.063 μA cm-2), uas yog sib xws nrog Rct tus nqi ntsuas los ntawm EIS. Thaum ob peb hnub thawj zaug, cov nqi impedance hauv P. Cov kua qaub aeruginosa nce ntxiv vim yog qhov txuas ntawm P. aeruginosa hlwb thiab kev tsim cov biofilms. Txawm li cas los xij, thaum cov biofilm npog tag nrho ntawm qhov chaw ntawm cov qauv, qhov impedance txo qis. Cov txheej tiv thaiv raug tawm tsam ua ntej vim yog qhov tsim ntawm biofilms thiab biofilm metabolites. Yog li ntawd, qhov kev tiv thaiv corrosion txo qis dhau sijhawm, thiab qhov txuas ntawm P. aeruginosa ua rau muaj kev xeb hauv zos. Cov qauv hauv abiotic media txawv. Qhov kev tiv thaiv corrosion ntawm cov kev tswj tsis yog biological siab dua li tus nqi sib xws ntawm cov qauv raug rau P. aeruginosa kua qaub. Ntxiv mus, rau cov qauv abiotic, tus nqi Rct ntawm 2707 HDSS tau txog 489 kΩ cm2 rau hnub 14, uas yog 15 npaug ntawm tus nqi Rct (32 kΩ cm2) nyob rau hauv lub xub ntiag ntawm P. aeruginosa. Yog li ntawd, 2707 HDSS muaj kev tiv thaiv corrosion zoo heev hauv ib puag ncig sterile, tab sis tsis tiv taus MIC tawm tsam los ntawm P. aeruginosa biofilms.
Cov txiaj ntsig no kuj tuaj yeem pom los ntawm cov kab polarization hauv daim duab 2b. Qhov kev sib txuas ntawm anodic tau raug suav hais tias yog Pseudomonas aeruginosa biofilm tsim thiab cov tshuaj tiv thaiv oxidation hlau. Tib lub sijhawm, qhov tshuaj tiv thaiv cathodic yog qhov txo qis ntawm oxygen. Qhov muaj P. aeruginosa ua rau muaj qhov ceev ntawm corrosion tam sim no ntau heev, kwv yees li qhov kev txiav txim siab siab dua li kev tswj hwm abiotic. Qhov no qhia tau hais tias P. aeruginosa biofilm ua rau muaj kev xeb hauv zos ntawm 2707 HDSS. Yuan et al29 pom tias qhov ceev ntawm corrosion tam sim no ntawm 70/30 Cu-Ni alloy nce ntxiv hauv qab kev sib tw ntawm P. aeruginosa biofilm. Qhov no yuav yog vim muaj biocatalysis ntawm kev txo qis oxygen los ntawm Pseudomonas aeruginosa biofilms. Qhov kev soj ntsuam no kuj tseem yuav piav qhia txog MIC ntawm 2707 HDSS hauv txoj haujlwm no. Aerobic biofilms kuj tseem yuav muaj oxygen tsawg dua hauv qab lawv. Yog li ntawd, qhov tsis ua tiav los rov ua kom cov hlau nto los ntawm oxygen yuav yog qhov ua rau MIC hauv txoj haujlwm no.
Dickinson et al. 38 tau hais tias cov nqi ntawm cov tshuaj lom neeg thiab electrochemical tshuag tuaj yeem cuam tshuam ncaj qha los ntawm kev ua haujlwm ntawm cov kab mob sessile ntawm qhov chaw ntawm cov qauv thiab qhov xwm txheej ntawm cov khoom xeb. Raws li pom hauv Daim Duab 5 thiab Rooj 5, ob qho tib si tus lej ntawm tes thiab biofilm tuab txo qis tom qab 14 hnub. Qhov no tuaj yeem piav qhia tau tias tom qab 14 hnub, feem ntau ntawm cov hlwb sessile ntawm qhov chaw ntawm 2707 HDSS tuag vim yog kev noj zaub mov tsis txaus hauv 2216E nruab nrab lossis kev tso tawm ntawm cov hlau ions lom los ntawm 2707 HDSS matrix. Qhov no yog qhov txwv ntawm kev sim ua pawg.
Hauv txoj haujlwm no, P. aeruginosa biofilm tau txhawb nqa qhov kev txo qis hauv zos ntawm Cr thiab Fe hauv qab biofilm ntawm 2707 HDSS nto (Daim Duab 6). Hauv Rooj 6, qhov kev txo qis ntawm Fe thiab Cr hauv cov qauv D piv rau cov qauv C, qhia tias Fe thiab Cr yaj los ntawm P. aeruginosa biofilm tseem nyob dhau 7 hnub thawj zaug. Lub nruab nrab 2216E siv los ua qauv ib puag ncig hauv dej hiav txwv. Nws muaj 17700 ppm Cl-, uas sib piv rau qhov pom hauv dej hiav txwv ntuj. Qhov muaj 17700 ppm Cl- yog qhov laj thawj tseem ceeb rau kev txo qis hauv Cr hauv 7- thiab 14-hnub abiotic kuaj los ntawm XPS. Piv rau P. aeruginosa cov qauv, qhov kev yaj ntawm Cr hauv cov qauv abiotic tsawg dua vim yog qhov muaj zog Cl− tsis kam ntawm 2707 HDSS hauv cov ib puag ncig abiotic. Daim Duab 9 qhia txog qhov muaj Cr6 + hauv zaj duab xis passivation. Nws yuav koom nrog hauv kev tshem tawm Cr ntawm cov hlau los ntawm P. aeruginosa biofilms, raws li Chen thiab Clayton tau hais.
Vim yog cov kab mob loj hlob, cov nqi pH ntawm cov khoom nruab nrab ua ntej thiab tom qab cog qoob loo yog 7.4 thiab 8.2, raws li. Yog li ntawd, hauv qab P. aeruginosa biofilm, cov organic acid corrosion tsis zoo li yuav yog ib qho tseem ceeb rau txoj haujlwm no vim yog pH siab heev hauv cov khoom nruab nrab loj. pH ntawm cov khoom nruab nrab tswj tsis tau hloov pauv ntau (los ntawm thawj 7.4 mus rau qhov kawg 7.5) thaum lub sijhawm xeem 14 hnub. Qhov nce hauv pH hauv cov khoom nruab nrab tom qab kev sib xyaw yog vim yog cov haujlwm metabolic ntawm P. aeruginosa thiab pom tias muaj tib yam cuam tshuam rau pH thaum tsis muaj cov ntawv xeem.
Raws li pom hauv Daim Duab 7, qhov tob tshaj plaws uas tshwm sim los ntawm P. aeruginosa biofilm yog 0.69 μm, uas loj dua li ntawm abiotic medium (0.02 μm). Qhov no yog sib xws nrog cov ntaub ntawv electrochemical piav qhia saum toj no. Qhov tob ntawm 0.69 μm yog ntau dua kaum npaug me dua li tus nqi 9.5 μm uas tau tshaj tawm rau 2205 DSS nyob rau hauv tib qho xwm txheej. Cov ntaub ntawv no qhia tau tias 2707 HDSS ua rau muaj kev tiv thaiv MIC zoo dua piv rau 2205 DSS. Qhov no yuav tsum tsis txhob xav tsis thoob, vim 2707 HDSS muaj cov ntsiab lus chromium siab dua, muab kev tiv thaiv ntev dua, vim yog cov qauv theem sib npaug tsis muaj cov khoom ua rau muaj kev phom sij, ua rau nws nyuaj rau P. aeruginosa kom depassivate thiab pib cov ntsiab lus eclipse.
Xaus lus, MIC pitting tau pom nyob rau ntawm qhov chaw ntawm 2707 HDSS hauv P. aeruginosa kua zaub piv rau qhov tsis tseem ceeb pitting hauv abiotic media. Cov haujlwm no qhia tau hais tias 2707 HDSS muaj kev tiv thaiv MIC zoo dua li 2205 DSS, tab sis nws tsis muaj zog tiv thaiv MIC tag nrho vim yog P. aeruginosa biofilm. Cov kev tshawb pom no pab xaiv cov hlau tsis xeb thiab kwv yees lub neej kev pabcuam rau ib puag ncig marine.
Daim coupon rau 2707 HDSS yog muab los ntawm Tsev Kawm Ntawv ntawm Metallurgy ntawm Northeastern University (NEU) hauv Shenyang, Suav. Cov khoom sib xyaw ntawm 2707 HDSS tau qhia hauv Rooj 1, uas tau soj ntsuam los ntawm NEU Materials Analysis thiab Testing Department. Tag nrho cov qauv tau kho cov tshuaj ntawm 1180 ° C rau 1 teev. Ua ntej kev sim xeb, npib-puab 2707 HDSS nrog thaj chaw saum toj kawg nkaus ntawm 1 cm2 tau polished rau 2000 grit nrog silicon carbide ntawv thiab ntxiv polished nrog 0.05 μm Al2O3 hmoov ncua. Cov sab thiab hauv qab yog tiv thaiv los ntawm inert xim. Tom qab ziab, cov qauv tau rinsed nrog sterile deionized dej thiab sterilized nrog 75% (v / v) ethanol rau 0.5 teev. Lawv tau cua-ziab nyob rau hauv ultraviolet (UV) lub teeb rau 0.5 teev ua ntej siv.
Tus kab mob Marine Pseudomonas aeruginosa MCCC 1A00099 tau yuav los ntawm Xiamen Marine Culture Collection Center (MCCC), Suav teb. Pseudomonas aeruginosa tau loj hlob aerobically ntawm 37°C hauv 250 ml flasks thiab 500 ml electrochemical iav hlwb siv Marine 2216E kua nruab nrab (Qingdao Hope Biotechnology Co., Ltd., Qingdao, Suav teb). Nruab nrab (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 SrBr2, 0.022 H3BO3, 0.004 NaSiO3, 0016 NH3, 0016 NH3, 0016 NaH2PO4, 5.0 peptone, 1.0 yeast extract thiab 0.1 ferric citrate. Ua kom sov ntawm 121°C rau 20 feeb ua ntej txhaj tshuaj. Suav cov hlwb sessile thiab planktonic siv lub hemocytometer hauv qab lub tshuab microscope ntawm 400X magnification. Qhov concentration ntawm planktonic Pseudomonas aeruginosa hauv cov hlwb thaum pib txhaj tshuaj tam sim ntawd yog kwv yees li 106 hlwb/ml.
Cov kev ntsuam xyuas electrochemical tau ua nyob rau hauv lub iav peb-electrode classic nrog qhov ntim nruab nrab ntawm 500 ml. Ib daim ntawv platinum thiab ib lub electrode calomel saturated (SCE) tau txuas nrog lub reactor ntawm Luggin capillaries puv nrog cov choj ntsev, ua haujlwm ua cov electrodes counter thiab reference, feem. Txhawm rau ua cov electrodes ua haujlwm, ib txoj hlua tooj liab-coated roj hmab tau txuas rau txhua tus qauv thiab npog nrog epoxy, tawm txog 1 cm2 ntawm thaj chaw ib sab rau lub electrode ua haujlwm. Thaum lub sijhawm ntsuas electrochemical, cov qauv tau muab tso rau hauv 2216E nruab nrab thiab khaws cia ntawm qhov kub thiab txias tas li (37 ° C) hauv lub dab dej da dej. OCP, LPR, EIS thiab cov ntaub ntawv polarization dynamic tau ntsuas siv Autolab potentiostat (Reference 600TM, Gamry Instruments, Inc., USA). LPR kev ntsuam xyuas tau kaw ntawm tus nqi scan ntawm 0.125 mV s-1 hla ntau ntawm -5 thiab 5 mV nrog Eocp thiab zaus kuaj ntawm 1 Hz. EIS tau ua nrog nthwv dej sine hauv zaus ntau yam 0.01 txog 10,000 Hz siv 5 mV siv hluav taws xob ntawm lub xeev ruaj khov Eocp. Ua ntej lub peev xwm cheb, cov electrodes tau nyob rau hauv hom qhib-circuit kom txog thaum muaj tus nqi ruaj khov corrosion dawb. Cov kab polarization ces khiav ntawm -0.2 txog 1.5 V vs. Eocp ntawm tus nqi scan ntawm 0.166 mV / s. Txhua qhov kev xeem tau rov ua dua 3 zaug nrog thiab tsis muaj P. aeruginosa.
Cov qauv rau kev tshuaj xyuas metallographic tau raug txhuam nrog 2000 grit ntub SiC daim ntawv thiab tom qab ntawd txhuam ntxiv nrog 0.05 μm Al2O3 hmoov suspension rau kev soj ntsuam optical. Kev tshuaj xyuas metallographic tau ua tiav siv lub tshuab microscope optical. Cov qauv tau etched nrog 10 wt.% potassium hydroxide kua 43.
Tom qab kev sib xyaw ua ke, cov qauv tau ntxuav 3 zaug nrog phosphate-buffered saline (PBS) kua (pH 7.4 ± 0.2) thiab tom qab ntawd kho nrog 2.5% (v/v) glutaraldehyde rau 10 teev kom kho cov biofilms. Tom qab ntawd nws tau qhuav nrog cov koob tshuaj ntsuam xyuas (50%, 60%, 70%, 80%, 90%, 95% thiab 100% v/v) ntawm ethanol ua ntej cua qhuav. Thaum kawg, qhov chaw ntawm cov qauv tau sputtered nrog ib zaj duab xis kub los muab conductivity rau SEM soj ntsuam. Cov duab SEM tau tsom mus rau cov chaw uas muaj cov hlwb P. aeruginosa sessile tshaj plaws ntawm qhov chaw ntawm txhua tus qauv. Ua EDS kev tshuaj xyuas kom pom cov tshuaj lom neeg. Ib lub Zeiss Confocal Laser Scanning Microscope (CLSM) (LSM 710, Zeiss, Lub Tebchaws Yelemees) tau siv los ntsuas qhov tob ntawm qhov av. Txhawm rau soj ntsuam cov qhov av xeb hauv qab biofilm, daim ntawv xeem tau ntxuav ua ntej raws li Suav Tebchaws Tus qauv (CNS) GB/T4334.4-2000 kom tshem tawm cov khoom xeb thiab biofilm ntawm qhov chaw ntawm daim ntawv xeem.
Kev tshuaj xyuas X-ray photoelectron spectroscopy (XPS, ESCALAB250 surface analysis system, Thermo VG, USA) tau ua tiav los ntawm kev siv lub monochromatic X-ray qhov chaw (kab txhuas Kα ntawm 1500 eV zog thiab 150 W zog) hla ntau qhov sib txuas zog 0 nyob rau hauv cov xwm txheej txheem -1350 eV. Cov spectra siab daws teeb meem tau kaw tseg siv 50 eV dhau zog thiab 0.2 eV kauj ruam loj.
Cov qauv uas tau muab tso rau hauv qhov chaw kuaj tau raug tshem tawm thiab yaug maj mam nrog PBS (pH 7.4 ± 0.2) rau 15 s45. Txhawm rau saib seb cov kab mob muaj sia nyob ntawm cov biofilms ntawm cov qauv, cov biofilms tau siv cov khoom siv LIVE/DEAD BacLight Bacterial Viability Kit (Invitrogen, Eugene, OR, USA). Cov khoom siv muaj ob hom xim fluorescent, ib qho xim ntsuab fluorescent SYTO-9 thiab ib qho xim liab fluorescent propidium iodide (PI). Hauv CLSM, cov dots nrog fluorescent ntsuab thiab liab sawv cev rau cov hlwb muaj sia thiab tuag, raws li. Rau kev siv cov xim, ib qho sib tov 1 ml uas muaj 3 μl SYTO-9 thiab 3 μl PI kua tau muab tso rau hauv qhov chaw kuaj rau 20 feeb ntawm chav tsev kub (23 oC) hauv qhov tsaus ntuj. Tom qab ntawd, cov qauv xim tau pom ntawm ob lub wavelengths (488 nm rau cov hlwb muaj sia thiab 559 nm rau cov hlwb tuag) siv lub tshuab Nikon CLSM (C2 Plus, Nikon, Nyiv). Qhov tuab ntawm Biofilm tau ntsuas hauv hom 3-D scanning.
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