Corrosion tus nqi yog ib qho kev ntsuas ntau yam uas nyob ntawm ob qho tib si ntawm ib puag ncig sab nraud thiab ntawm cov khoom sab hauv ntawm cov khoom. Nyob rau hauv cov ntaub ntawv normative thiab technical, muaj qee yam kev txwv ntawm qhov tso cai ntawm cov hlau puas tsuaj thaum lub sijhawm ua haujlwm ntawm cov khoom siv thiab cov qauv tsim kom ntseeg tau tias lawv tsis muaj teeb meem kev ua haujlwm. Hauv engineering, tsis muaj universal txoj kev los txiav txim tus nqi corrosion. Qhov no yog vim qhov nyuaj ntawm kev coj mus rau hauv tus account txhua yam. Txoj kev ntseeg siab tshaj plaws yog kawm txog keeb kwm kev ua haujlwm ntawm lub chaw.
cwj pwm
Tam sim no, ntau tus nqi corrosion yog siv hauv engineering tsim:
- Raws li txoj kev ntsuas ncaj qha: txo qhov loj ntawm ib feem ntawm cov hlau ib chav tsev - qhov taw qhia qhov hnyav (ntsuas hauv grams ib 1 m 2rau 1 teev); kev puas tsuaj tob (los yog corrosion txheej txheem permeability), mm / xyoo; tus nqi ntawm cov roj tso tawm theem ntawm corrosion khoom; qhov ntev ntawm lub sij hawm thaum lub sij hawm thawj corrosion puas tshwm sim; tus naj npawb ntawm cov chaw corrosion nyob rau hauv ib cheeb tsamCov chaw uas tau tshwm sim dhau ib lub sijhawm.
- Kev kwv yees ncaj qha: electrochemical corrosion tam sim no lub zog; hluav taws xob tsis kam; hloov ntawm lub cev thiab cov yam ntxwv ntawm txhua yam.
thawj qhov ntsuas qhov ntsuas ncaj qha yog qhov ntau tshaj.
Calculation formulas
Hauv cov ntaub ntawv dav dav, qhov poob phaus uas txiav txim siab qhov corrosion ntawm cov hlau yog pom los ntawm cov qauv hauv qab no:
Vkp=q/(St), qhov twg q yog qhov txo qis ntawm cov hlau, g;
S - thaj chaw uas cov khoom raug xa mus, m2;
t - lub sijhawm, teev
Rau cov ntawv hlau thiab cov plhaub ua los ntawm nws, txiav txim siab qhov ntsuas qhov tob (mm / xyoo):
H=m/t, m yog qhov tob ntawm kev nkag mus rau hauv cov hlau.
Muaj kev sib raug zoo hauv qab no ntawm thawj thiab thib ob ntsuas tau piav qhia saum toj no:
H=8, 76Vkp/ρ, qhov twg ρ yog qhov ntom ntawm cov khoom.
Lub ntsiab tseem ceeb cuam tshuam rau tus nqi corrosion
Cov pab pawg hauv qab no cuam tshuam rau tus nqi ntawm kev puas tsuaj hlau:
- sab hauv, cuam tshuam rau lub cev thiab tshuaj lom neeg ntawm cov khoom (theem qauv, tshuaj lom neeg muaj pes tsawg leeg, nto roughness ntawm ib feem, residual thiab kev khiav hauj lwm stresses nyob rau hauv cov khoom, thiab lwm yam);
- sab nraud (ib puag ncig, nrawm ntawm kev txav ntawm qhov nruab nrab corrosive, kub, muaj pes tsawg leeg ntawm huab cua, muaj cov inhibitors lossis stimulants, thiab lwm yam);
- mechanical (kev txhim kho ntawm cov kab nrib pleb, kev puas tsuaj ntawm cov hlau nyob rau hauv qhov kev txiav txim ntawm cyclic loads,cavitation thiab fretting corrosion);
- tsim nta (xaiv qib hlau, qhov sib txawv ntawm qhov chaw, qhov xav tau roughness).
Lub cev thiab tshuaj lom neeg
Qhov tseem ceeb tshaj plaws hauv kev txhim kho corrosion yog cov hauv qab no:
- Thermodynamic stability. Txhawm rau txiav txim siab nws hauv cov kev daws teeb meem aqueous, siv Pourbaix daim duab siv, raws li abscissa axis uas pH ntawm nruab nrab yog plotted, thiab raws li ordinate axis, lub peev xwm redox. Lub peev xwm hloov pauv hauv qhov kev taw qhia zoo txhais tau tias muaj kev ruaj ntseg ntau dua ntawm cov khoom siv. Tentatively, nws yog txhais raws li ib txwm equilibrium peev xwm ntawm cov hlau. Qhov tseeb, cov ntaub ntawv corrode ntawm tus nqi sib txawv.
- Txoj haujlwm ntawm ib lub atom nyob rau hauv lub sij hawm lub sij hawm ntawm cov ntsiab lus tshuaj. Cov hlau feem ntau raug rau corrosion yog alkali thiab alkaline ntiaj teb hlau. Tus nqi ntawm corrosion txo qis raws li tus lej atomic nce.
- Crystal qauv. Nws muaj qhov tsis meej pem txog kev puas tsuaj. Cov qauv ntxhib-grained nws tus kheej tsis ua rau muaj kev txhim kho corrosion, tab sis yog qhov zoo rau kev txhim kho ntawm intergranular xaiv kev puas tsuaj ntawm cov ciam teb. Hlau thiab alloys nrog ib homogeneous tis ntawm theem corrode tusyees, thaum cov uas tsis yog-uniform faib corrode raws li ib tug focal mechanism. Kev sib koom ua ke ntawm cov theem ua haujlwm ntawm cov anode thiab cathode nyob rau hauv ib puag ncig nruj.
- Lub zog tsis sib xws ntawm cov atoms hauv cov iav siv lead ua. Atoms nrog lub zog siab tshaj plaws nyob rau ntawm cov ces kaum ntawm lub ntsej muagmicroroughnesses thiab yog qhov chaw ua haujlwm ntawm kev tawg thaum lub sij hawm tshuaj corrosion. Yog li ntawd, ceev faj machining ntawm cov hlau qhov chaw (sib tsoo, polishing, xov) tsub kom corrosion kuj. Cov nyhuv no kuj tau piav qhia los ntawm kev tsim cov denser thiab txuas ntxiv oxide zaj duab xis rau ntawm qhov chaw du.
Influence of medium acidity
Nyob rau hauv cov txheej txheem ntawm tshuaj corrosion, qhov concentration ntawm hydrogen ions cuam tshuam cov ntsiab lus hauv qab no:
- solubility ntawm cov khoom siv corrosion;
- tsim cov yeeb yaj kiab tiv thaiv oxide;
- metal destruction rate.
Thaum pH nyob rau hauv thaj tsam ntawm 4-10 units (acidic tov), corrosion ntawm hlau nyob ntawm qhov siv ntawm oxygen nkag mus rau saum npoo ntawm cov khoom. Hauv cov tshuaj alkaline, tus nqi corrosion ua ntej txo qis vim yog qhov chaw passivation, thiab tom qab ntawd, ntawm pH >13, nce ntxiv los ntawm kev tawg ntawm cov yeeb yaj kiab tiv thaiv oxide.
Rau txhua hom hlau muaj nws tus kheej dependence ntawm kev siv ntawm kev puas tsuaj ntawm acidity ntawm cov tshuaj. Noble hlau (Pt, Ag, Au) yog resistant rau corrosion nyob rau hauv ib tug acidic ib puag ncig. Zn, Al raug puas tsuaj sai nyob rau hauv ob qho tib si acids thiab alkalis. Ni thiab Cd tiv taus alkalis tab sis corrode yooj yim hauv acids.
Kev sib xyaw thiab kev sib xyaw ntawm cov kev daws teeb meem nruab nrab
Tus nqi ntawm corrosion nyob rau hauv nruab nrab cov ntsiab lus nyob ntawm ntau yam ntawm cov ntsev thiab nws cov concentration:
- Thaum lub sijhawm hydrolysis ntawm ntsev hauvNyob rau hauv ib puag ncig corrosive, ions yog tsim los ua activators lossis retarders (inhibitors) ntawm hlau puas.
- Cov tebchaw uas nce pH kuj nce tus nqi ntawm cov txheej txheem kev puas tsuaj (piv txwv li, dej qab zib tshauv), thiab cov uas txo cov acidity txo nws (ammonium chloride).
- Nyob rau hauv lub xub ntiag ntawm chlorides thiab sulfates nyob rau hauv cov kev daws, kev puas tsuaj yog qhib kom txog thaum ib tug tej yam concentration ntawm ntsev mus txog (uas tau piav qhia los ntawm kev siv zog ntawm cov txheej txheem anode nyob rau hauv tus ntawm chloride thiab sulfur ions), thiab tom qab ntawd maj mam txo qis vim qhov txo qis hauv cov dej solubility ntawm oxygen.
Qee hom ntsev muaj peev xwm tsim tau ib zaj duab xis insoluble (piv txwv li, hlau phosphate). Qhov no pab tiv thaiv cov hlau los ntawm kev puas tsuaj ntxiv. Cov cuab yeej no yog siv thaum siv cov tshuaj tiv thaiv xeb.
Corrosion inhibitors
Corrosion inhibitors (los yog inhibitors) txawv hauv lawv cov txheej txheem ntawm kev ua ntawm cov txheej txheem redox:
- Anode. Ua tsaug rau lawv, ib zaj duab xis passive yog tsim. Cov pab pawg no suav nrog cov tebchaw raws li chromates thiab bichromates, nitrates thiab nitrites. Hom kawg ntawm inhibitors yog siv rau kev tiv thaiv kev tiv thaiv ntawm qhov chaw. Thaum siv anodic corrosion inhibitors, nws yog ib qho tsim nyog yuav tsum tau ua ntej txiav txim siab lawv qhov kev tiv thaiv tsawg kawg nkaus, txij li kev ntxiv me me tuaj yeem ua rau muaj qhov nce ntawm kev puas tsuaj.
- Cathode. Cov txheej txheem ntawm lawv qhov kev ua yog ua raws li qhov txo qis hauv cov pa oxygen thiab, raws li, kev qeeb hauv cov txheej txheem cathodic.
- Kev tiv thaiv. Cov inhibitors no cais cov hlau nto los ntawm kev tsim cov tshuaj insoluble uas tau tso ua txheej tiv thaiv.
Pab pawg kawg suav nrog cov tshuaj tiv thaiv xeb, uas tseem siv los ntxuav oxides. Lawv feem ntau muaj phosphoric acid. Nyob rau hauv nws cov cawv, hlau phosphating tshwm sim - tsim muaj zog tiv thaiv txheej ntawm insoluble phosphates. Neutralizers yog siv nrog rab phom los yog cov menyuam. Tom qab 25-30 feeb, qhov saum npoo tau txais cov xim dawb-grey. Tom qab cov tshuaj dries, cov xim thiab cov kua roj vanish yog siv.
Mechanical action
Kev nce hauv corrosion nyob rau hauv ib qho kev txhoj puab heev yog yooj yim los ntawm cov hom kev ua haujlwm xws li:
- Internal (thaum lub sij hawm molding los yog kev kho cua sov) thiab sab nraud (nyob rau hauv tus ntawm ib tug externally thov load) stresses. Yog li ntawd, electrochemical inhomogeneity tshwm sim, lub thermodynamic stability ntawm cov khoom txo, thiab corrosion cracking yog tsim. Tshwj xeeb tshaj yog ceev yog kev puas tsuaj nyob rau hauv tensile loads (kav yog tsim nyob rau hauv perpendicular dav hlau) nyob rau hauv lub xub ntiag ntawm oxidizing anions, piv txwv li, NaCl. Ib qho piv txwv ntawm cov cuab yeej raug rau hom kev puas tsuaj no yog qhov chaw ntawm chav boilers.
- Kev hloov pauv hloov pauv, kev vibration (corrosion qaug zog). Muaj qhov txo qis hauv kev qaug zog, ntau qhov microcracks yog tsim, uas tom qab ntawd ua ke rau hauv ib qho loj. Tus lejLub voj voog mus rau qhov tsis ua tiav ntau dua nyob ntawm cov tshuaj thiab theem ntawm cov hlau thiab alloys. Twj axles, springs, turbine blades thiab lwm yam khoom yog raug rau xws li corrosion.
- Kev sib txhuam ntawm qhov chaw. Kev xeb nrawm yog vim kev siv tshuab ntawm cov yeeb yaj kiab tiv thaiv ntawm qhov chaw thiab tshuaj lom neeg cuam tshuam nrog ib puag ncig. Hauv cov kua, tus nqi ntawm kev puas tsuaj yog qis dua hauv huab cua.
- Cavitation cuam tshuam. Cavitation tshwm sim thaum qhov txuas ntxiv ntawm cov kua ntws tau ua txhaum vim yog qhov tsim ntawm lub tshuab nqus tsev npuas uas tawg thiab tsim cov nyhuv pulsating. Yog li ntawd, kev puas tsuaj tob ntawm ib qho chaw hauv zos tshwm sim. Hom kev xeb no feem ntau pom hauv cov cuab yeej tshuaj.
Design Factors
Thaum tsim cov khoom ua haujlwm hauv cov xwm txheej hnyav, nws yuav tsum tau coj mus rau hauv tus account tias tus nqi corrosion nce hauv cov xwm txheej hauv qab no:
- thaum cov hlau tsis sib xws tuaj rau hauv kev sib cuag (qhov ntau dua qhov sib txawv ntawm cov electrode muaj peev xwm ntawm lawv, qhov siab dua lub zog tam sim no ntawm cov txheej txheem electrochemical ntawm kev puas tsuaj);
- nyob rau hauv lub xub ntiag ntawm cov neeg kho tshuab kev ntxhov siab concentrators (grooves, grooves, qhov, thiab lwm yam);
- nrog kev ua kom huv si tsawg ntawm cov tshuab ua haujlwm, vim qhov no tshwm sim hauv zos luv luv-circuited galvanic khub;
- nrog qhov sib txawv ntawm qhov kub thiab txias ntawm ib tus neeg ntawm lub cuab yeej (tshav kub galvanic hlwb raug tsim);
- nyob rau hauv lub xub ntiag ntawm stagnant aav (slots, khoob);
- thaum tsimresidual stresses, tshwj xeeb tshaj yog nyob rau hauv welded pob qij txha (kom tshem tawm lawv, nws yog tsim nyog los muab kev kho cua sov - annealing).
kev ntsuas ntsuas
Muaj ntau txoj hauv kev los ntsuas tus nqi ntawm kev puas tsuaj ntawm cov hlau hauv qhov chaw nruj:
- Laboratory - kuaj cov qauv hauv cov xwm txheej simulated ze rau qhov tiag. Lawv qhov zoo dua yog tias lawv tso cai rau koj txo lub sijhawm kawm.
- Teb - tuav hauv tej yam ntuj tso. Lawv siv sijhawm ntev. Qhov zoo ntawm txoj kev no yog tau txais cov ntaub ntawv hais txog cov khoom ntawm cov hlau hauv cov xwm txheej ntawm kev ua haujlwm ntxiv.
- Kev ntsuas hauv qhov chaw ntawm cov khoom hlau tiav hauv ib puag ncig ntuj.
