Vim li cas thiaj li muaj cov kab xeb los ntawm Carbon Steel Upstream Drastically Accelerate Galvanic Corrosion of Titanium Heater's End Cap hauv Brine?

Titanium immersion heaters feem ntau yog ua hauj lwm nyob rau hauv brine systems nrog upstream carbon steel piping, tso tsheb hlau luam los yog tshav kub exchangers. Nyob rau hauv brine, carbon hlau yog raug rau tej yam ntuj tso corrosion, uas ua rau xeb hais, feem ntau hlau oxides (Fe2O3, Fe3O4) thiab oxyhydroxides. Cov khoom no raug thauj nrog cov dej ntws ntawm brine thiab nws thiaj li tso rau ntawm qhov chaw hauv lub cev xws li lub hau kawg ntawm lub tshuab cua sov titanium. Lub hau kawg feem ntau yog welded kaw thaum kawg ntawm lub raj cua sov, feem ntau tsim los ntawm tib qib ntawm titanium tab sis nrog qhov sib txawv ntawm qhov tiav. Nyob rau hauv ib qho electrolyte (brine), xeb particles uas tso rau ntawm titanium tsim ib tug galvanic cell. Hauv cov tshuaj chloride, xeb yog electrochemically noble rau titanium nrog ib tug so muaj peev xwm 200-400 mV ntau zoo. Qhov tshwm sim yog ceev hauv zos corrosion ntawm titanium nyob ib puag ncig txhua qhov xeb uas ua rau pitting thiab qhov kawg perforation ntawm lub hau kawg.

Electrochemical Mechanism ntawm Galvanic Corrosion Induced los ntawm xeb

Titanium nyob rau hauv 3–5% NaCl brine muaj ib tug passive peev xwm ntawm kwv yees li ntawm +0.1 rau +0.3 V vs. Ag/AgCl vim nws TiO₂ txheej. Rust particles, tshwj xeeb tshaj yog magnetite (Fe3O4), yog semiconductive thiab muaj peev xwm sib xyaw ntawm +0.5 rau +0.7 V vs. Ag/AgCl. Tom qab ntawd lub voj voog raug kaw los ntawm cov electrolyte thaum muaj xeb particle hits titanium nto. Cov kab xeb xeb ua haujlwm ua cov cathode, qhov chaw txo cov pa oxygen: O₂ + 2H₂O + 4e⁻ → 4OH⁻ Cov titanium nyob ib sab ntawm cov particle ua raws li anode thiab dissolves li Ti⁴⁺. Lub cheeb tsam anodic yog heev kaw, feem ntau nyob rau hauv 1-2 particle diameters los ntawm xeb deposits. Txhawm rau kom yaj cov titanium ntawm tus nqi ntawm 1-5 hli hauv ib xyoos, qhov ceev tam sim no ntawm anode tuaj yeem siab li 1-5 mA / cm2. Lub hau kawg yog qhov tshwj xeeb tshaj plaws, vim nws feem ntau yog qhov sib txawv ntawm qhov chaw tiav (raws li welded piv rau cov raj xa dej), thiab tej zaum yuav muaj cov kab nrib pleb ntawm cov ntiv taw uas xeb tuaj yeem sau tau.

Quantification ntawm acceleration ntawm corrosion tus nqi los ntawm xeb hais

Tus nqi corrosion ntawm Qib 2 titanium kawg cap daim coupon hauv 5% NaCl brine ntawm 50℃raws li kev tswj xyuas qhov chaw tau txiav txim siab rau cov kab mob hauv qab no:

Ntxuav brine, tsis muaj xeb hais: Passive tam sim no ceev 0.05-0.10 µA / cm2. Corrosion tus nqi tsawg dua 0.01 hli / xyoo. Lub hau kawg tseem ci ntsa iab thiab tsis muaj -corroded tom qab 5,000 teev.

Rust hais siv ntawm 10 ppm, ntws tsis tu ncua: Corrosion tus nqi ntawm 0.08-0.15 hli ib xyoos. localized pitting ntawm qhov chaw sib cuag nrog qhov tob ntawm 20-50 µm tom qab 1000 teev.

Cov kab xeb tuaj yeem nce qhov kev sib txhuam corrosion mus rau 0.3-0.6 hli / xyoo ntawm 50 ppm. Qhov tob ntawm 100-200 µm tom qab 1000 h. Lub hau kawg muaj qhov pom tseeb tsis muaj xim nyob ib puag ncig cov particle deposits.

Ntxiv cov khoom xeb ntawm 200 ppm, ntws: Corrosion tus nqi 1.0-2.0 mm / xyoo Lub qhov tob tom qab 1000 h yog nyob rau hauv thaj tsam ntawm 300-600 µm. End cap perforation ntawm 1.0 hli phab ntsa 500 rau 1,000 teev.

Kev daws cov kab xeb ntawm kab rov tav kawg cap (stagnant deposit) Local corrosion rate> 5 mm/yr. Ua kom tiav perforation ntawm 1.2 hli txheem kawg hau hauv 3-6 lub hlis. Sib sib zog nqus pitting penetrates weld tshav kub cuam tshuam cheeb tsam.

Kev Tiv Thaiv Lub Tswv Yim ntawm Qhov Kawg Cap rau Kev Tshaj Tawm rau Cov Kab Xev

Cov lus hauv qab no muab cov ntoo txiav txim siab rau kev tiv thaiv titanium rhaub kawg lub kaus mom nyob rau hauv cov xwm txheej ntawm cov pa roj carbon steel corrosion thiab brine ntws.

Upstream Carbon Steel Condition & Brine Flow Pom Zoo Kawg Cap Protection StrategyFigure 2. Core Rationale & Galvanic Corrosion Mitigation
New carbon steel with less corrosion and high flow (>1 m / s) Txheem, du weld tiav, Qib 2 kawg capFlow inhibits qhov teeb meem ntawm cov khoom. Txais kev pheej hmoo rau 3 mus rau 5 xyoo kev pab cuam lub neej
Hnub nyoog carbon steel nrog me me corrosion (50-100 ppm), intermittent flowEnd cap nrog PTFE txheej (0.5 hli tuab) Cov txheej hluav taws xob insulates titanium los ntawm xeb hais. Txheej txhua 2 xyoos.
Heavy corrosion upstream (>200 ppm), tsis tshua muaj ntws/stagnant zonesEnd cap tsim nrog tus kheej -tu txoj kab nqes (min 45℃).Sloped End Cap Nres Particle Build-Up. Tsis muaj dab tsi kab rov tav. Txhim kho cov dej ntws ntws los txhawm rau txhawm rau txhawm rau xeb.
Lub tshuab hluav taws xob uas twb muaj lawm nrog lub hau kawg uas qhia cov pob txha pob txha So kom huv tam sim ntawd nrog 5% citric acid thiab nruab sacrificial zinc anode. Zinc anode (10 g) siv rau lub hau kawg rov qab cov galvanic khub. Txhua xyoo anode hloov.
Cov kev pabcuam tseem ceeb uas lub tshuab cua sov tsis tuaj yeem zam tau Qib 7 titanium kawg cap nrog electropolished tiav Kev suav nrog palladium txhim kho titanium lub peev xwm thiab txo cov tsav tsheb rau galvanic corrosion. Qhov siab tshaj plaws kev cia siab.
Engineering Beyond End Cap Protection

Qhov kev tiv thaiv theem nrab yog qhov kawg ntawm phab ntsa thickness Qhov loj kawg cap (2.0 hli vs 1.2 hli) nce lub sij hawm rau perforation tab sis tsis txo corrosion tus nqi. Qhov kawg cap geometry yog qhov tseem ceeb tshaj, domed lossis conical kawg lub kaus mom tso cov khoom, lub hau kawg lub kaus mom sau cov nyiaj tso cia. Lub weld nruab nrab ntawm lub raj thiab lub hau kawg yuav tsum du thiab tsis muaj fissures qhov twg cov khoom tuaj yeem raug daig. Kev lim dej ntws tawm kom tshem tawm cov xeb uas loj dua 50 µm tuaj yeem ua rau lub neej kawg ntawm 5 txog 10. Magnetite yog ferrimagnetic . Yog li ntawd, ib tug sib nqus cuab nyob rau hauv lub brine kab upstream ntawm lub rhaub yuav selectively extract magnetite hais.

Ua ib qho kev qhia tshwj xeeb

Thaum tsim lub titanium rhaub rau brine kev pab cuam downstream ntawm carbon steel Cheebtsam, muaj xws li ib tug yuav tsum tau rau upstream particle filtration (50 µm nominal) los yog ib tug sib nqus separator. Xaiv lub domed lossis conical kawg cap es tsis txhob ntawm lub hau kawg. Kev teeb tsa uas twb muaj lawm: tshuaj xyuas lub kaus mom kawg peb lub hlis twg siv borescope. Yog hais tias xeb- xim deposits muaj, ntxuav sai sai nrog ib tug qaug zog acid (5% citric los yog 10% acetic acid), thiab xyuas pitting qhov tob nrog ib tug ultrasonic thickness gauge. Rau cov kev teeb tsa tshiab hauv cov xwm txheej hnyav hnyav, qhia Qib 7 titanium rau lub tshuab ua kom tiav nrog rau lub hau kawg thiab ntxiv cov zinc anode txuas rau lub hau kawg nrog lub titanium hlau. Lub zinc anode polarizes titanium mus rau ntau dua qhov tsis zoo thiab tshem tawm cov galvanic tsav quab yuam nrog xeb hais. Los ntawm kev daws qhov teeb meem ntawm cov kab mob xeb ntawm cov kab ke, tus kws ua haujlwm zam qhov ceev ceev, muaj zog hauv zos corrosion uas feem ntau ua rau ntxov ntxov kawg lub hau tsis ua hauj lwm nyob rau hauv txwv tsis pub corrosion{11}}resistant titanium heaters.