Nyob rau hauv ib qho tshuaj etching da dej uas muaj hydrofluoric thiab nitric acids, titanium qib twg (los yog lwm yam hlau) yuav tsum hloov qib 2 kom ciaj sia tshaj 48 teev?
Tso lus
Cov tshuaj etching da dej rau titanium thiab stainless hlau feem ntau muaj cov sib xyaw ntawm hydrofluoric acid (HF) thiab nitric acid (HNO₃). HF muab cov kev sib tsoo hnyav ntawm cov hlau hauv paus, thaum HNO₃ ua tus neeg sawv cev oxidizing los tswj cov tshuaj tiv thaiv thiab txhim kho saum npoo. Ib qho kev sib xyaw ua ke yog 10% HF + 20% HNO₃ hauv dej, ua haujlwm ntawm 25-40℃. Qib 2 titanium, txawm tias nws zoo heev corrosion kuj nyob rau hauv ntau qhov chaw, dissolves sai heev nyob rau hauv HF- bearing kev daws teeb meem. Cov tshuaj fluoride ion complexes nrog titanium ions thiab tiv thaiv kev tsim cov zaj duab xis passive. Nyob rau hauv ib tug raug etching da dej, Qib 2 titanium poob 0.5-1.0 hli ntawm phab ntsa thickness ib teev, ua kom tiav perforation ntawm tus qauv 1.2 hli raj nyob rau hauv 2-3 teev. Txhawm rau kom muaj sia nyob ntev dua 48 teev ntawm kev sib xyaw ua ke, cov khoom sib txawv -xws li cov titanium alloy tshwj xeeb lossis lwm yam hlau- yuav tsum tau xaiv.
Mechanism of Rapid Qib 2 Titanium Attack hauv HF/HNO₃ Mixtures
Hauv HF- muaj cov kev daws teeb meem, cov yeeb yaj kiab TiO₂ passive dissolves tam sim no: TiO₂ + 6F⁻ + 4H⁺ → TiF₆²⁻ + 2H₂O. Tsis muaj kev tiv thaiv zaj duab xis, lub hauv paus titanium hlau corrodes nquag. Nitric acid nyob rau hauv qhov sib tov tsis repassivate titanium vim fluoride ions txuas ntxiv tshem tawm cov oxide uas tsim. Cov tshuaj tiv thaiv corrosion yog sib xws thiab ceev: Ti + 6HF → TiF₆²⁻ + 2H⁺ + 2H₂. Cov tshuaj tiv thaiv hydrogen evolution kuj tseem nrawm los ntawm HF. Qhov tshwm sim yog ib tug linear khoom poob tus nqi uas tsis muaj lub sij hawm incubation. Qib 2, Qib 7, thiab Qib 12 titanium txhua tus muaj titanium ua cov hlau hauv paus, yog li txhua tus raug kev txom nyem zoo sib xws hauv HF / HNO₃ sib tov.
Kev ua tau zoo ntawm Alternative Titanium Qib hauv HF / HNO₃
Kev ntsuas immersion nyob rau hauv 10% HF + 20% HNO₃ ntawm 30℃tau tsim cov nqi hauv qab no:
Qib 2 (kev lag luam ntshiab): Corrosion npaum li cas ntawm 0.8 hli ib teev . 1.2 hli raj perforated hauv 1.5 teev. Tsis haum tshaj ib zaug - siv cov cua sov uas siv tau pov tseg.
Qib 7 (Ti-0.15Pd): Corrosion npaum li cas ntawm 0.7 hli ib teev. Palladium tsis muaj txiaj ntsig vim tias muaj txiaj ntsig zoo ntawm cov hlau catalysis yuav tsum muaj cov yeeb yaj kiab tsis zoo, uas tsis tuaj. Zoo ib yam li Qib 2.
Qib 12 (Ti-0.3Mo-0.8Ni): Corrosion npaum li cas ntawm 0.6 hli ib teev. Molybdenum thiab npib tsib xee ntxiv muab kev txhim kho marginal tab sis tsis txaus rau 48-teev ciaj sia taus.
Qib 5 (Ti-6Al-4V): Corrosion npaum li cas ntawm 0.5 hli ib teev. Lub alpha-beta microstructure dissolves nyiam nyob rau ntawm beta theem ciam teb, ua rau intergranular nres. Tsis pom zoo.
Alternative Metal Selection for HF/HNO₃ Service
Cov lus hauv qab no muab kev sib piv ntawm lwm cov hlau uas tuaj yeem muaj sia nyob 48 teev lossis ntau dua hauv HF / HNO₃ etching da dej:
| Hlau los yog Alloy | Corrosion Rate hauv 10% HF+20% HNO₃ ntawm 30℃(mm / xyoo) | Lub sij hawm nkag mus rau phab ntsa 1.5 hli | Kev Ua Haujlwm Zoo Tshaj Plaws HF% | Tus nqi Index (Qib 2=1.0) |
|---|---|---|---|---|
| Tantalum (tsis muaj) | 0.05mm / xyoo | 30, 000+ teev (3.4+ xyoo) | Txog li 60% HF | 15–20 |
| Zirconium (R60702) | 0.08mm / xyoo | 18,750 teev (2.1 xyoo) | Txog li 50% HF | 8–10 |
| Hastelloy C-276 | 1.2 hli / xyoo | 1.25 teev (75 feeb) | Tsis pom zoo | 3–4 |
| Siab- silicon cam khwb cia hlau (Duriron) | 0.3 hli / xyoo | 5,000 teev (7 lub hlis) | Txog li 15% HF | 2–3 |
| PTFE (polymer, tsis yog hlau) | 0.00 hli / xyoo (tshuaj inert) | Unlimited (mechanical zog txwv) | Ib qho | 1.5-2 (nrog kev txhawb nqa hlau) |
| Tantalum{0}}clad titanium | Ib yam li tantalum (0.05 mm / xyoo) | 30, 000+ teev | Txog li 60% HF | 10–12 |
Daim Ntawv Qhia Xaiv Tswv Yim rau 48-teev Ciaj sia nyob yuav tsum tau
Rau lub tshuab cua sov uas yuav tsum muaj sia nyob 48 teev ntawm kev tso rau hauv HF / HNO₃ etching da dej, cov khoom siv yuav tsum muaj qhov corrosion qis dua li ntawm 0.03 mm / teev (0.03 mm / hr × 48 hr=1.44 mm nkag). Tsuas yog tantalum, zirconium, thiab PTFE ua tau raws li qhov yuav tsum tau ua:
Tantalum: Qhov zoo tshaj plaws corrosion kuj. Ua kom ruaj khov Ta₂O₅ zaj duab xis uas tiv thaiv HF txog li 60% hauv qab 50 degree. Ua haujlwm kub siab tshaj plaws ntawm 150 degree. Tus nqi siab tab sis muaj kev pabcuam ntau xyoo. Weldable thiab fabricable.
Zirconium: Kev xaiv zoo heev nrog tus nqi qis. Tiv thaiv HF los ntawm kev tsim ib zaj duab xis ZrO₂ uas ruaj khov dua TiO₂ hauv fluoride media. Qhov siab tshaj plaws HF concentration ntawm 50% ntawm 30 degree. Ua rau pitting yog tias nitric acid concentration poob qis dua 10%.
PTFE (polytetrafluoroethylene): Chemically inert to HF/HNO₃ mixs. Siv raws li ib tug liner tshaj ib tug hlau substrate (feem ntau yog carbon steel los yog titanium rau cov qauv kev txhawb nqa). Ua haujlwm kub siab tshaj plaws ntawm 200 degree. Thermal conductivity tsawg heev (0.25 W/m·K vs. 21 W/m·K rau titanium), yog li cov cua sov yuav tsum tau loj dua qhov chaw.
Ua ib qho kev qhia tshwj xeeb
Thaum qhia txog lub rhaub rau HF/HNO₃ etching da dej uas yuav tsum tau muaj sia nyob tshaj 48 teev, tsis txhob xaiv cov qib titanium. Qib 2, Qib 7, thiab Qib 12 tag nrho ua tsis tiav hauv ib teev. Rau cov ntawv thov uas tus nqi yog qhov thib ob thiab kev ntseeg siab yog qhov tseem ceeb, qhia txog lub tshuab hluav taws xob tantalum immersion. Rau cov nqi ntau dua- cov ntawv thov nkag siab, qhia lub zirconium rhaub nrog phab ntsa thickness ntawm 2.0 hli yam tsawg kawg nkaus. Rau qhov kev xaiv tus nqi qis tshaj plaws uas tseem ua tiav 48-teev ciaj sia taus, qhia PTFE-jacketed titanium rhaub qhov twg PTFE muab tshuaj tiv thaiv (0.5-1.0 hli thickness) thiab titanium muab kev txhawb nqa. Thov los ntawm tus neeg muag khoom daim ntawv pov thawj corrosion nyob rau hauv qhov tshwj xeeb HF / HNO₃ ratio thiab kub ntawm lub npaj da dej. Thaum lub sijhawm ua haujlwm, saib xyuas HF concentration txhua hnub; nce siab tshaj 15% HF nce corrosion tus nqi ntawm zirconium los ntawm ib qho ntawm 10. Los ntawm kev xaiv lwm yam hlau es tsis yog sim hloov cov qib titanium, tus kws ua choj ua kom ntseeg tau tias cov cua sov ua tau zoo nyob rau hauv ib qho ntawm ob peb qhov chaw uas titanium yog qhov tsis tsim nyog.
