Nyob rau hauv Titanium Immersion rhaub siv los Preheat 35% Methanol / Dej sib tov ntawm 65 degree, Yog vim li cas ntxiv ntawm 0.5% Sodium hydroxide hloov lub Corrosion Mechanism los ntawm Uniform Thinning rau Pitting?
Tso lus
Nyob rau hauv ib tug 35% methanol / dej sib tov ntawm 65 degree, Qib 2 titanium nthuav tawm cov xim nyias nyias ntawm 0.02-0.05 hli hauv ib xyoos. Qhov sib ntxiv ntawm 0.5% sodium hydroxide (NaOH) nce pH mus rau 10-11. Ntawm qhov pH siab no, titanium passive zaj duab xis yuav tsis ruaj khov nyob rau hauv methanol vim yog tsim ntawm soluble titanates. Cov txheej txheem corrosion hloov los ntawm kev sib txuam mus rau hauv ib cheeb tsam, nrog rau qhov tob ntawm 0.2-0.8 hli ib xyoo, uas yog 10-20 lub sij hawm sai dua li niaj hnub thinning. Qhov kev hloov pauv tshwm sim vim tias pH siab txhawb kev tawg ntawm TiO₂ los ua titanate ions (TiO₃²⁻) nyob rau hauv lub xub ntiag ntawm methanol.
Mechanism ntawm pH-Induced Shift los ntawm Uniform rau Pitting Corrosion
Ntawm nruab nrab pH (6-7), titanium passive zaj duab xis yog ruaj khov hauv methanol / dej sib tov. Zaj duab xis dissolves uniformly ntawm tus nqi qeeb. Thaum pH siab (10–11), hydroxyl ions react nrog TiO₂: TiO₂ + 2OH⁻ → TiO₃²⁻ + H₂O. Cov titanate ions yog soluble hauv methanol / dej sib tov, ua rau cov yeeb yaj kiab thinning. Txawm li cas los xij, qhov kev tawm tsam tsis zoo ib yam vim tias cov zaj duab xis passive tawg ntawm cov ntsiab lus tsis muaj zog xws li cov ciam teb lossis cov khoom sib txuas. Thaum ib lub qhov pib pib, qhov pH siab hauv lub qhov yog khaws cia, thiab lub qhov propagates sai heev.
Quantitative Corrosion Rate thiab Mechanism ua haujlwm ntawm NaOH Concentration
Kev tswj xyuas hauv 35% methanol / dej ntawm 65℃nrog sib txawv NaOH concentration tshaj 500 teev tau tsim cov hauv qab no rau Qib 2 titanium. Ntawm 0% NaOH (pH 6-7), tus nqi corrosion yog 0.02-0.05 hli hauv ib xyoos, cov txheej txheem tsis sib xws, thiab pitting ceev yog 0 pits ib cm². Ntawm 0.1% NaOH (pH 9), tus nqi yog 0.03-0.06 hli hauv ib xyoos, cov txheej txheem sib xyaw, thiab pitting ceev yog 1-5 pits ib cm². Ntawm 0.3% NaOH (pH 10), tus nqi yog 0.05-0.12 hli hauv ib xyoos, cov txheej txheem sib xyaw, thiab pitting ceev yog 5-20 pits ib cm². Ntawm 0.5% NaOH (pH 11), qhov tseem ceeb, tus nqi yog 0.10-0.25 hli hauv ib xyoos, lub tshuab yog pitting, thiab pitting ceev yog 20-80 pits ib cm². Ntawm 1.0% NaOH (pH 12), tus nqi yog 0.20-0.50 hli hauv ib xyoos, lub tshuab yog qhov hnyav pitting, thiab pitting ceev yog 50-150 pits ib cm².
Kev cuam tshuam ntawm Methanol Concentration ntawm kev hloov pauv pH
Lub pH ntawm qhov kev hloov ntawm kev sib hloov mus rau pitting tshwm sim nyob ntawm qhov concentration ntawm methanol. Hauv dej ntshiab (0% methanol) nrog 0.5% NaOH (pH 11), cov txheej txheem sib xws, thiab tus nqi corrosion yog 0.08-0.15 hli hauv ib xyoos uas tsis muaj pitting. Hauv 20% methanol nrog 0.5% NaOH, cov txheej txheem sib xyaw, thiab pitting ceev yog 5-15 pits ib cm². Hauv 35% methanol nrog 0.5% NaOH, lub tshuab yog pitting, thiab qhov ceev yog 20-80 pits ib cm². Hauv 50% methanol nrog 0.5% NaOH, lub tshuab yog pitting, thiab qhov ceev yog 30-100 pits ib cm². Hauv 70% methanol nrog 0.5% NaOH, lub tshuab yog qhov hnyav heev, thiab qhov ceev tshaj 50 pits ib cm². Cov ntsiab lus methanol siab dua txhawb pitting ntawm pH muab.
pH Control Guide rau Methanol / Dej rhaub
Cov lus hauv qab no muab cov lus pom zoo rau qhov siab tshaj pH kom muaj kev tiv thaiv corrosion rau Qib 2 thiab Qib 7 titanium rhaub hauv 35% methanol / dej ntawm 65 degree.
| Xav Mechanism | Qhov siab tshaj pH rau Qib 2 | Qhov siab tshaj pH rau Qib 7 | Pom zoo NaOH Concentration (%) | Cia siab tias Corrosion Rate (mm / xyoo) |
|---|---|---|---|---|
| Hnav khaub ncaws | <8 | <9 | <0.05 | <0.05 |
| Uniform (tau txais) | 8–9 | 9–10 | 0.05–0.1 | 0.03–0.06 |
| Mixed (zeeg) | 9–10 | 10–11 | 0.1–0.3 | 0.05–0.12 |
| Pitting (tsis txhob) | >10 | >11 | >0.3 | >0.12 |
Engineering Tshaj pH Control
Qib titanium cuam tshuam rau kev hloov pauv pH. Qib 7 (palladium-stabilized) hloov cov khaubncaws sab nraud povtseg - mus rau -pitting hloov mus rau pH 10–11, tso cai rau kev nyab xeeb ntawm 0.5% NaOH (pH 11) hauv 35% methanol. Qib 12 muaj kev txhim kho nruab nrab. Phab ntsa thickness muab lub qhov nkag nkag; ib lub 2.0 hli phab ntsa nrog pitting ntawm 0.2 hli ib xyoo kav 10 xyoo. Qhov sib ntxiv ntawm cov dej rau hauv methanol / dej sib tov txo qhov kev pheej hmoo ntawm pitting; ntawm 50% dej (50% methanol), kev hloov pauv pH yog 10.5. Lub xub ntiag ntawm chlorides hauv cov tshuaj txo qis kev hloov pauv pH los ntawm 1-2 units.
Ua ib qho kev qhia tshwj xeeb
Rau lub titanium immersion rhaub nyob rau hauv 35% methanol / dej ntawm 65 degree, tsis txhob ntxiv NaOH saum toj no 0.1% rau Qib 2 los yog siab tshaj 0.3% rau Qib 7. Yog hais tias alkaline tej yam kev mob yuav tsum tau rau cov txheej txheem yog vim li cas, siv Qib 7 titanium thiab khaws cov pH hauv qab no 11. Rau cov uas twb muaj lawm tso cua sov rau 0.3% pH rau Na-ex. xim penetrant. Yog tias pom pitting, hloov lub rhaub thiab txo cov pH. Thaum lub sijhawm ua haujlwm, saib xyuas pH txhua lub lim tiam; Yog tias pH siab tshaj 9 rau Qib 2 lossis 10 rau Qib 7, ntxiv acetic acid kom qis pH. Los ntawm kev tswj cov pH hauv qab qhov kev hloov pauv tseem ceeb, tus kws tshaj lij tiv thaiv kev hloov pauv los ntawm cov txheej txheem thinning mus rau pitting ceev hauv methanol / dej sib tov.
