** Hauv qib 2 titanium cua sov raj raug kub 10% ferric chloride + 5% hydrochloric acid zoo hlau rov qab tov ntawm 60 degree, dab tsi tsawg kawg nkaus phab ntsa thickness tiv thaiv pitting ntawm cov kua -vapor interface rau 3000 teev ntawm kev pab cuam intermittent?**
Qib 2 titanium cua sov raj tau nce ntxiv rau cov hlau muaj nuj nqis rov qab los ntawm cov khoom siv hluav taws xob siv ferric chloride -hydrochloric acid daws uas muaj 10% ferric chloride (FeCl₃) thiab 5% hydrochloric acid (HCl) ntawm 60℃. Cov tshuaj no yog oxidizing heev vim Fe³⁺, uas tswj cov titanium's passive zaj duab xis nyob rau hauv tag nrho immersed tej yam kev mob. Txawm li cas los xij, ib qho kev tsis ua haujlwm tshwj xeeb tshwm sim ntawm cov kua -vapor interface - thaj av uas lub raj cua sov dhau los ntawm qhov chaw daws teeb meem. Thaum lub sijhawm ua haujlwm tsis sib xws (cov cua kub cua sov nrog lub sijhawm txias), qhov kev sib tshuam ntsib kev ntub dej - caij tsheb kauj vab qhuav, uas muaj cov tshuaj chloride ntsev rau ntawm titanium nto. Kev sib xyaw ua ke ntawm cov tshuaj chlorides, cov pa oxygen los ntawm huab cua sib cuag, thiab thermal cycling ua rau ib puag ncig hnyav dua li qhov kev mob siab rau tag nrho. Lub pitting tus nqi ntawm lub interface yog 5-10 lub sij hawm siab tshaj nyob rau hauv cov kev daws teeb meem. Kev txiav txim siab qhov tsawg kawg nkaus phab ntsa tuab uas muab 3000 teev ntawm kev pabcuam sib cuam tshuam yam tsis muaj perforation ntawm lub interface yuav tsum nkag siab txog kev sib raug zoo ntawm chloride concentration factor thiab pitting propagation rate.
**Mechanism of Liquid-Vapor Interface Pitting**
Ntawm cov kua-vapor interface, titanium passive zaj duab xis tau rov ua dua. Thaum immersed, cov tshuaj FeCl₃ / HCl tswj kom ruaj khov TiO₂ zaj duab xis. Thaum raug vapors thaum lub sij hawm tawm - lub voj voog lossis thaum qhov kev daws teeb meem poob qis, cov yeeb yaj kiab nyias nyias evaporates, tsom rau ferric chloride thiab hydrochloric acid rau ntawm titanium nto. Cov concentrated brine txo qis pH hauv zos thiab nce cov tshuaj chloride los ntawm qhov zoo ntawm 10-20. Thaum rov-immersion, cov ntsev ntsev yaj sai sai, tab sis cov zaj duab xis passive tej zaum yuav raug cuam tshuam. Rov ua dua cov voj voog ua rau qhov pib pitting hauv zos. Thaum ib lub qhov dej nucleates, cov chemistry nyob rau hauv lub qhov yuav depleted ntawm Fe³⁺ (lub passivating oxidizer) thiab enriched nyob rau hauv Cl⁻, tiv thaiv repassivation. Lub qhov propagates los ntawm phab ntsa thickness. Rau 0.8 hli phab ntsa, lub qhov tob txog 0.6 hli ua rau perforation nyob rau hauv siab. Rau ib lub 1.2 hli phab ntsa, tib lub qhov yuav tsum propagate ntxaum, thiab vim hais tias lub qhov propagation accelerates nrog qhov tob, cov ntaub ntawv ntxiv muab disproportionate lub neej extension.
**Quantitative Pitting Propagation ntawm Interface**
Kev tswj xyuas siv qib 2 titanium raj (12 hli OD, ntau cov phab ntsa thicknesses) raus hauv 10% FeCl₃, 5% HCl ntawm 60℃nrog cyclic ntub- tej yam kev mob qhuav (8 teev raus dej, 16 teev raug vapor, rov ua dua) qhia txog kev coj cwj pwm hauv qab no {{8} vapor interface
| Phab ntsa Thickness (mm)|Chloride Concentration Factor ntawm Interface|Sijhawm rau Pit Initiation (teev)|Pit Propagation Rate tom qab pib (hli ib 1000 teev)|Sijhawm rau Perforation (teev)|Tag Nrho Kev Pabcuam Lub Neej (teev)|Safe rau 3000h? |
|---------------------|-------------------------------------------|-------------------------------|-----------------------------------------------------------|-----------------------------|----------------------------|-----------------|
| 0.5|15 – 20 ×|150 – 250|0.45 – 0.65 Nws 600 – 900|750 – 1,150|Tsis muaj |
| 0.6|15 – 20 ×|180 – 300|0.40–0.55 Nws 750 – 1,100|930 – 1,400|Tsis muaj |
| 0.7|15 – 20 ×|200 – 350|0.35 – 0.50 Nws 900 – 1,300|1,100 – 1,650|Tsis muaj |
| 0.8|15 – 20 ×|220–400 : kuv 0.30 – 0.45 dr hab 1,100 – 1,600|1,320 – 2,000|Tsis muaj |
| 0.9|15 – 20 ×|250 – 450|0.25–0.38 Nws 1,300 – 1,900|1,550 – 2,350|Tsis muaj |
| 1.0|15 – 20 ×|280–500 : kuv 0.20 – 0.32 Nws 1,600 – 2,300|1,880 – 2,800|Marginal |
| 1.2|15 – 20 ×|320–550 : kuv 0.15 – 0.25 dr hab 2,100 – 3,000|2,420 – 3,550|Yog (thov txim) |
| 1.5|15 – 20 ×|380 – 600 Ib 0.10 – 0.18|3,000 – 4,500|3,380 – 5,100|Yog (safe) |
Cov ntaub ntawv qhia tau hais tias 1.2 hli phab ntsa muab qhov nruab nrab kev pab cuam lub neej ntawm kwv yees li 3,000 teev, thaum lub 0.8 hli phab ntsa tsis nyob ntawm kwv yees li 1,650 teev - qhov sib txawv ntawm 1.8 ×. 1.2 hli phab ntsa ua tau raws li 3000-teev lub hom phiaj, thaum 0.8 hli tsis zoo luv.
** Yog vim li cas lub interface yog nruj dua li tej kev daws teeb meem **
Cov tshuaj chloride concentration ntawm 15-20 × ntawm lub interface yog tus thawj tsav tsheb ntawm ceev pitting. Hauv 10% FeCl₃, 5% HCl, cov tshuaj chloride ntau yog kwv yees li 6-8% (1.7-2.2 M). Ntawm qhov sib txuas thaum lub voj voog ziab, cov tshuaj chloride tuaj yeem ncav cuag 10-15 M. Ntawm cov concentrations no, cov zaj duab xis passive ntawm qib 2 titanium tsis ruaj khov, thiab pitting muaj peev xwm hloov mus rau qhov tseem ceeb hauv qab lub peev xwm corrosion. Tsis tas li ntawd, cov pa oxygen los ntawm huab cua sib cuag thaum lub sij hawm ziab kom rov ua dua cov cathodic reactant, tuav lub siab corrosion tam sim no. Kev sib xyaw ua ke ntawm cov tshuaj chloride concentrated, huab cua sib cuag, thiab thermal cycling ua rau qhov sib cuam tshuam 5-10 npaug ntau dua li cov tshuaj ntau.
**Scenario-Raws li Phau Ntawv Qhia Xaiv: Phab Ntsa Thickness rau E-Cov Cuab Yeej Siv Hluav Taws Xob**
| Kev Ua Haujlwm|Interface Cycle zaus|Pom Zoo Phab Ntsa Thickness (mm)|Cia Siab Interface Lub Neej (teev)|Engineering Justification |
|--------------------|--------------------------|-------------------------------|--------------------------------|----------------------------|
| Cov kev pabcuam sib cuam tshuam, 3000-teev phiaj xwm|8h on / 16h tawm|1.2|2,400 – 3,500|Raws li 3000-teev lub hom phiaj ntawm qhov nruab nrab |
| Continuous service (no level fluctuation) | None | 0.7 – 0.8 | >5,000|Tsis muaj interface nres yog tias tag nrho raus |
| Kev caij tsheb kauj vab ntau zaus (hloov qib hloov pauv)|1h on / 1h tawm|1.5|3,000 – 4,500|Kev sib tw nruj dua yuav tsum muaj phab ntsa tuab dua |
| Extended campaign (>5000 teev)|8h on / 16h tawm|1.5|3,500 – 5,000|Conservative tsim rau siab tshaj plaws kev ntseeg |
| Short- lub sijhawm ua haujlwm (<1000 hours) | 8h on / 16h off | 0.7 | 1,100 – 1,650 | Acceptable for temporary service |
| Interface cheeb tsam tiv thaiv los ntawm PTFE txheej|8h on / 16h tawm|0.7 – 0.8|3,000 – 5,000|Txheej tshem tawm ntub - voj voog qhuav |
** Kev ntsuas ntxiv kom txo tau qhov cuam tshuam cuam tshuam **
Peb ntsuas txo pitting ntawm lub interface yam tsis tau nce phab ntsa thickness. Ua ntej, tswj cov qib kev daws teeb meem tas li siv tus tswj qib uas ua kom lub tshuab cua sov rau txhua lub sijhawm; qhov no tshem tawm cov ntub dej - lub voj voog qhuav tag. Thib ob, siv PTFE txheej rau thaj chaw sib cuam tshuam (50 hli ntu ntawm cov kua kab); cov txheej tiv thaiv kev sib cuag ncaj qha ntawm cov ntsev ntsev thiab cov titanium nto, tshem tawm cov kev sib tshuam pitting. Thib peb, rau qib 2 tshuab, hloov mus rau qib 7 titanium (0.15% Pd) ntawm tib phab ntsa tuab; lub palladium muab kev hloov kho cathodic uas hloov lub peev xwm pitting mus rau qhov muaj txiaj ntsig zoo dua, txuas ntxiv lub neej cuam tshuam los ntawm 2-3 ×. Qib 7 raj nrog 0.8 hli phab ntsa muab lub neej sib npaug rau qib 2 nrog 1.2 hli phab ntsa.
**Qhov xaus**
Rau qib 2 titanium cua sov raj hauv 10% ferric chloride, 5% hydrochloric acid tov ntawm 60℃rau cov hlau zoo zoo rov qab los ntawm e- khib nyiab, qhov tsawg kawg nkaus phab ntsa thickness ntawm 1.2 hli yuav tsum tau ua kom tiav 3000 xuab moos ntawm kev pab cuam sib tshuam yam tsis muaj perforation ntawm cov kua - vapor interface Lub interface tau ntsib cov tshuaj chloride concentration ntawm 15–20 × vim yog ntub dej - caij tsheb kauj vab qhuav, tsim pitting tus nqi 5-10 npaug siab dua hauv cov tshuaj ntau. Lub phab ntsa 0.8 hli tsis pub dhau 1650-2000 teev, thaum 1.2 hli muab lub neej nruab nrab ntawm 3000 teev. Cov kws tsim qauv qhia txog titanium cov cua sov rau e- khib nyiab rov qab yuav tsum xaiv 1.2 hli raws li qhov tsawg kawg nkaus rau cov txheej txheem sib cuam tshuam kev pabcuam, siv qib tswj lossis PTFE txheej txhawm rau tshem tawm kev cuam tshuam cuam tshuam, lossis xav txog qib 7 titanium rau cov phab ntsa nyias nyias nrog lub neej sib npaug. Qhov no phab ntsa thickness specification tiv thaiv qhov tseem ceeb tsis ua hauj lwm hom nyob rau hauv chlorinated acid rov ua hauj lwm.
