Yuav Ua Li Cas Qhov Kev Pom Zoo ntawm Copper Ions (100 ppm) hauv qhov sov, Aerated Sulfuric Acid Solution (10%) Accelerate Galvanic Corrosion ntawm Titanium Heating Tube ntawm Welded Joints?

Kev lag luam yooj yim- tawm hauv titanium rhaub tsim rau tooj liab kab mob sulfuric acid
Dilute sulfuric acid (10% H 2 SO 4) ntawm 60-80℃feem ntau yog ua hauj lwm hauv tooj liab electrowinning, pickling ntawm tooj liab alloys thiab tshuaj ntxuav ntawm tshav kub exchanger. Titanium feem ntau yog passive nyob rau hauv 10% H2SO4 qis dua 80℃nrog corrosion tus nqi ntawm 0.01-0.05 hli / xyoo vim hais tias mus rau zus tau tej cov titanium dioxide txheej. Txawm li cas los xij, lub xub ntiag ntawm yaj Cu{13}} ions nyob rau theem qis li 100 ppm hloov cov corrosion electrochemistry profoundly. Copper ions ua hauj lwm raws li ib tug zoo cathodic depolarizer, raug hloov mus rau hlau tooj liab (Cu²⁺ + 2e⁻ → Cu⁰) nyob rau saum npoo ntawm titanium, tsim ib tug ntxeem tau tooj liab deposits. Qhov no tooj liab tso nyiaj ua ib khub galvanic nrog lub hauv paus titanium, nrog titanium ua tus anode thiab tooj liab raws li noble cathode. Ntawm cov pob qij txha welded, titanium microstructure yog heterogeneous vim lub tshav kub cuam tshuam cheeb tsam (HAZ) thiab cov nyhuv galvanic yog tsom, ua rau muaj zog hauv zos. Phab ntsa thickness ntawm lub titanium rhaub tube dictates ntau npaum li cas cov khoom muaj los tiv thaiv no localized corrosion, tab sis qhov yooj yim phenomenon yog electrochemical thiab tsis tuaj yeem raug tshem tawm los ntawm tsuas yog thickening phab ntsa. Qhov kev ua haujlwm no ntsuas qhov galvanic acceleration factor vim tooj liab ions thiab piav qhia txog qhov tsis ua haujlwm ntawm cov pob qij txha hauv cov tooj liab uas muaj sulfuric acid.

Cov nyhuv ntawm Mechanical Integrity: Galvanic Mechanism thiab Weld Microstructure
Hauv 10% H₂SO₄ ntawm 70℃yam tsis muaj tooj liab ions, qib 2 titanium muaj peev xwm corrosion ntawm li +0.1 V vs. SHE (Standard Hydrogen Electrode) thiab cov zaj duab xis passive yog khaws cia. Lub cathodic txo ntawm Cu 2+ rau Cu 0 nyiam tshwm sim nyob rau saum npoo ntawm titanium nyob rau hauv lub xub ntiag ntawm Cu 2+ ions, whereupon ib nyias (1-5 µm) tooj liab txheej yog deposited nyob rau hauv ob peb teev tom qab immersion. Cov nyiaj tso nyiaj tooj liab ua haujlwm raws li cathode thiab nce lub peev xwm corrosion ntawm titanium txog li +0.3 V vs. SHE, muaj txiaj ntsig ntau dua li qhov muaj peev xwm ua tau. Cov tooj liab tso nyiaj, txawm li cas los xij, tsis tas mus li thiab ua raws li qhov zoo. Galvanic hlwb raug tsim los ntawm qhov tsis zoo hauv txheej tooj liab (xws li cov ntiv taw ntiv taw, khawb lossis cov khoom sib txuas) qhov twg cov titanium raug anodic rau cov tooj liab nyob ib puag ncig. Lub galvanic tam sim no ceev ntawm lub anode yog 100-500 microA / cm^2 piv rau passive tam sim no ceev<1 microA/cm^2 in copper free acid. This current corresponds to a titanium dissolving rate of 0.5 to 2.5 mm per year at the anode sites. Welded joints are especially sensitive, because the HAZ has a distinct grain structure and may contain secondary phases (for example, beta phase stabilized by iron impurities) that are more active than the base metal. Weld reinforcement (extra weld metal) also forms a fissure like shape that retains copper deposits and prevents their removal by fluid flow. The galvanic acceleration and the microstructural heterogeneity generate preferential attack at the weld toe, which then propagates inwards. At a weld flaw a local corrosion rate of 1.5 mm per year would penetrate a wall of 1.2 mm in 9-10 months, although the base metal would remain largely unattacked.

Thermal Performance Impact: Galvanic Kinetics Kub Acceleration
Tus nqi ntawm galvanic corrosion ntawm deposited tooj liab thiab titanium yog Arrhenius nrog ib tug ua kom muaj zog ntawm ib ncig ntawm 30-40 kJ / mol. Qhov kub ntawm qhov kub ntawm 60 mus rau 80 degrees ua rau muaj kev nce ntxiv hauv cov galvanic tam sim no ntom ntom ntawm 2.5-3.0. Rau lub tshuab cua sov titanium khiav ntawm lub zog ceev ntawm 2.5 W / cm2 lub plhaub saum npoo kub yog feem ntau 5-12 C saum toj no cov kua qaub kub nyob ntawm phab ntsa tuab. Rau 1.0 hli phab ntsa hauv 70℃bulk acid, qhov kub ntawm qhov chaw yog li 76℃thiab rau 1.6 hli phab ntsa yog li 80 degree. Qhov 4℃qhov sib txawv no nce tus nqi galvanic corrosion los ntawm kwv yees li 30% thiab qee qhov cuam tshuam qhov kev tiv thaiv corrosion ntxiv los ntawm phab ntsa tuab. Qhov tseem ceeb tshaj, cov tshuaj tiv thaiv tooj liab tso tawm nws tus kheej yog qhov kub thiab txias. Qhov kub ntawm qhov chaw siab dua txhim kho Cu 2+ txo tus nqi uas ua rau cov tooj liab tuab dua thiab ntau dua. Cov thicker deposits muab loj dua qhov chaw cathodic, yog li nce qhov piv ntawm anode rau cathode cheeb tsam thiab tsav galvanic tam sim no ntau dua. Electrochemical impedance spectroscopy thwmsim qhia tau hais tias cov galvanic tam sim no ceev ntawm 80 {\\deg}C saum npoo kub yog 1.5 npaug ntawm siab tshaj ntawm 70 \\deg}C, muab tib yam tooj liab concentration. Yog li ntawd, qhov kub ntau dua ntawm cov phab ntsa tuab ua haujlwm tuaj yeem ua rau muaj kev xeb ntau dua ntawm cov vuam, tsis zoo rau cov txiaj ntsig zoo ntawm cov khoom siv ntxiv.

Lag luam-tawm Synthesis: Galvanic Corrosion Rate ntawm Welded Joints
Cov matrix hauv qab no qhia cov ntaub ntawv galvanic corrosion rau welded raj ntawm Qib 2 titanium hauv 10% H2SO4 nrog 100 ppm Cu2+ (raws li CuSO4) ntawm 70℃tej qhov kub thiab txias, lub zog ceev 2.5 W / cm2. Corrosion tus nqi tau txais nyob rau ntawm qhov chaw weld tshav kub cuam tshuam (HAZ) uas yog qhov chaw muaj kev cuam tshuam tshaj plaws rau kev ua phem galvanic.

Phab ntsa Thickness (mm) Sab Nraud Temp (degree) Galvanic Corrosion Rate nyob rau hauv Weld HAZ (mm/xyoo) Lub Sijhawm rau Perforation ntawm Weld (hli) Base Hlau Corrosion Rate (mm/xyoo) Failure Location 0.9 mm 75℃1.8 mm/xyoo 6 hli 0.10 mm/xyoo Weld 7 mm/year perforation Lub hli 0.10 hli / xyoo Weld ntiv taw perforation 1.3 hli 78℃2.1 hli / xyoo 7.5 hli 0.12 hli / xyoo Weld ntiv taw perforation
1.5 hli 79o C 2.2 hli / xyoo 8 hli 0.12 hli / xyoo Weld ntiv taw perforation
1.8 hli 81℃2.5 hli / xyoo 8.5 hli 0.15 hli / xyoo Weld ntiv taw perforation 2.0 hli (seamless, tsis muaj weld) 82℃Tsis siv tau (tsis muaj vuam)> 5 xyoos (lub hauv paus hlau xwb) 0.18 hli / xyoo Uniform thinning nkaus xwb
Cov ntaub ntawv qhia tau hais tias qhov tshwm sim ntawm qhov tsis ua hauj lwm qhov chaw thiab lub sij hawm yog nyob ntawm qhov muaj nyob ntawm welded junction thiab tsis nyob rau ntawm phab ntsa thickness. Tag nrho cov welded raj ntawm phab ntsa thickness ntawm 0.9 hli thiab 2.0 hli poob nyob rau hauv weld HAZ nyob rau hauv 6 - 9 lub hlis vim galvanic acceleration los ntawm tooj liab deposits. Txawm li cas los xij, lub raj seamless ntawm tib qib titanium (tsis muaj welded hlws ris) pom tsuas yog cov corrosion ntawm 0.15-0.18 hli / xyoo, thiab nrog 2.0 hli phab ntsa nws muaj lub neej ntawm 5+ xyoo. Qhov nce hauv lub sij hawm perforation nrog nce phab ntsa thickness ntawm 6 mus rau 8.5 lub hlis yog ib yam nkaus thiab coj los them rau cov phab ntsa tuab. Lub vuam, tsis yog phab ntsa tuab, yog qhov teeb meem tseem ceeb.

Sab nraum phab ntsa Engineering: Copper tshem tawm thiab Weld Elimination
Lub galvanic acceleration mechanism yog nyob rau hauv welded pob qij txha, yog li qhov zoo tshaj plaws counter ntsuas yog cov uas tshem tawm cov weld los yog tiv thaiv tooj liab deposition. Ua ntej, qhov cuam tshuam HAZ tuaj yeem raug tshem tawm tag nrho los ntawm kev qhia txog seamless titanium tubing (kos, tsis muaj longitudinal welds), thiab los ntawm kev siv flanged los yog threaded connectors es tsis txhob welded kawg kaus mom. Nyob rau hauv cov hlab seamless lub niaj hnub galvanic tam sim no kis mus rau tag nrho cov nto thiab corrosion tus nqi yog me me (0.15-0.20 mm / xyoo). Seamless tooj liab raj nrog lub thickness ntawm 1.2 hli yuav kav ntev li ntawm 5 mus rau 6 xyoo nyob rau hauv polluted sulfuric acid. Qhov thib ob, cov tooj liab tso nyiaj yog yaj ua ntej galvanic cell yog tsim los ntawm kev tshem tawm tooj liab los ntawm immersing lub rhaub hauv 5% nitric acid ntawm 50℃rau 30 feeb txhua 2-4 lub lis piam. Txawm tias cov cua sov welded tuaj yeem kav ntev li 2-3 xyoos nrog kev pab cuam tu txij li lub voj voog tiv thaiv tawg tsis tu ncua galvanic nres. Thib peb, qhov sib ntxiv ntawm cov tshuaj tiv thaiv corrosion xws li benzotriazole (BTA, 10-50 ppm) ua rau tsim cov txheej tiv thaiv ntawm cov tooj liab deposits, uas passivates lub cathodic nto thiab txo cov galvanic tam sim no los ntawm 80-90%. "BTA feem ntau siv rau hauv kev ua tooj liab thiab yog sib xws nrog sulfuric acid. Cov txiaj ntsig tau los ntawm kev ua haujlwm ntawm tooj liab electrowinning qhia tau hais tias 20 ppm BTA txo qhov vuam HAZ corrosion ntawm 2.0 hli hauv ib xyoos mus rau 0.3 hli hauv ib xyoos, nce lub neej ntawm lub tshuab cua sov los ntawm 6 lub hlis mus rau ntau tshaj 3 xyoos.

Xaus: Phab ntsa thickness tsis yog cov tshuaj, Weld Elimination lossis Copper Control yog
Lub galvanic corrosion acceleration ntawm ib tug titanium cua sov raj nyob rau hauv ib tug sov aerated 10% sulfuric acid tov nrog 100 ppm tooj liab ions yog nyob rau hauv lub welded pob qij txha, qhov twg tooj liab deposits tsim ib tug galvanic cell, uas ua rau lub zos tawm tsam ntawm 1.8-2.5 hli ib xyoo. Ua kom cov phab ntsa thickness ntawm 0.9 hli mus rau 2.0 hli tsuas yog nce lub sij hawm rau perforation ntawm lub weld los ntawm 6 lub hlis mus rau 8.5 lub hlis, ib tug me me kev pab cuam uas tsis pom zoo rau cov khoom ntxiv nqi thiab thermal nplua. Txoj hauv kev yooj yim yog tshem tawm cov welded hlws ris tag nrho los ntawm kev siv seamless titanium tubing uas ncav cuag 5+ xyoo ntawm kev pab cuam lub neej ntawm 1.2 hli phab ntsa thickness, los yog tswj cov deposition ntawm tooj liab los ntawm periodic acid tu los yog kev koom tes ntawm ib tug benzotriazole inhibitor. Thaum qhia txog tooj liab kuab paug sulfuric acid cov ntsiab lus tseem ceeb tsis yog phab ntsa tuab tab sis xav tau kev tsim kho seamless (ASTM B861, qib seamless) thiab kev pom zoo tu niaj hnub los yog inhibitor ntxiv. Lub tshuab cua sov welded yuav poob ntawm qhov vuam hauv ib xyoos txawm tias cov phab ntsa tuab npaum li cas. Lub tshuab cua sov seamless nrog ib txwm phab ntsa ntawm 1.2 hli yuav zoo dua li cov welded rhaub ntawm txhua phab ntsa tuab. Qhia rau cov chaw tsim khoom ntawm qhov xav tau ntawm tooj liab ion concentration (ppm) thiab muaj peev xwm ntawm kev tu ncua sij hawm. Nug kom paub tseeb tias lub rhaub muaj seamless tubing uas tsis muaj longitudinal los yog circumferential welds nyob rau hauv lub rhuab cheeb tsam.