Tsev / Kev Lag Luam Paub Txog Encyclopedia / Cov Ntsiab Lus Thaum Qib 2 Titanium rhaub yog siv los ua kom sov 50% Sodium Acetate Solution ntawm 90 degree, Dab tsi yog qhov siab tshaj plaws ntawm Acetic Acid Impurity (ppm) Ua ntej Hydrogen Evolution Initiates Blistering?

Sodium acetate (CH3COONa) 50% ntawm 90 degree, rau textile dyeing thiab tsis. Cov tshuaj yog alkaline (pH 8-9). Lub pH yog txo los ntawm acetic acid impurity los ntawm hydrolysis los yog paug. Thaum pH qis dua 5, cov txheej txheem tsis zoo ntawm titanium yuav tsis ruaj khov thiab cov txheej txheem cathodic hloov pauv los ntawm kev txo qis oxygen mus rau hydrogen evolution. Atomic hydrogen tuaj yeem nkag mus rau hauv titanium lattice thiab tsim molecular hydrogen nyob rau hauv qhov khoob, ua rau blistering ntawm qhov chaw. Qhov siab tshaj plaws acetic acid impurity yog 500 ppm (0.05%) los tiv thaiv hydrogen blistering. Nyob rau theem no, pH yog<5 and blisters occur within 100–500 hours.

Hydrogen Blistering hauv Acetate Solutions-Mechanism

Cov txheej txheem cathodic hauv alkaline sodium acetate yog txo cov pa oxygen thiab tsis tsim cov hydrogen atoms. Acetic acid poob pH: CH₃COOH → CH₃CO⁻ + H⁺. Ntawm pH < 5, cov tshuaj tiv thaiv hydrogen evolution 2H⁺ + 2e⁻ → H₂ yog qhov zoo rau thermodynamically. Lub atomic hydrogen intermediate (H) yog tsim ntawm titanium nto. Qee cov atomic hydrogen recombine rau hauv H_2 roj tab sis ib feem diffuse rau hauv titanium lattice. Hydrogen atoms diffuse mus rau hauv qhov sib txawv, inclusions los yog grain ciam teb thiab muaj recombine los tsim H_2 roj. Gas siab tsim thiab nto hlwv tuaj yeem tsim thiab tawg.

Quantitative Blistering ua haujlwm ntawm Acetic Acid Concentration

Kev tswj xyuas hauv 50% sodium acetate ntawm 90℃rau 500 teev nrog kev hloov pauv acetic acid impurity tau tsim cov hauv qab no. Ntawm acetic acid qis dua 100 ppm, pH yog 8.5-9.0, tsis muaj hydrogen evolution, tsis muaj hlwv thiab lub ntsej muag ci. Ntawm 100-300 ppm pH yog 6.0-7.5, cov kab mob hydrogen evolution yuav tshwm sim tab sis tsis muaj cov hlwv pom tseeb . 300-500 ppm 5.0-6.0 300-500 teev Qee zaus cov pob me me (<0.5 mm diameter) 1-5 per cm2 Blister density At 500–1,000 ppm the pH is 4.0–5.0, considerable blistering is observed with blister size 0.5–2 mm, blister density is 5–20 per cm² and blistering starts within 100–300 hours. Blistering occurs at concentrations above 1,000 ppm at pH levels below 4.0 with blister size greater than 2 mm, blister density greater than 20 per cm² and initiation of blistering in 50–150 hours.

Qhov cuam tshuam ntawm Kub thiab Oxygen Concentration ntawm Blistering Threshold

Qhov siab tshaj plaws tso cai acetic acid poob tawm nrog nce kub. Tso cai acetic acid ntawm 70℃yog 1000 ppm (0.1%). Ntawm 80℃nws yog 750 ppm . 500 ppm ntawm 90℃. Ntawm 100℃nws yog 300ppm. Nws yog 150 ppm ntawm 110 degree. Qhov chaw pib kuj cuam tshuam los ntawm qhov nyiaj ntawm cov pa oxygen. Thaum qis qis ntawm acetic acid, blistering tshwm sim hauv cov kev daws teeb meem vim tias tsis muaj oxygen txo qis los sib tw nrog hydrogen evolution. Aerated daws (O2> 5 ppm) nce cov acetic acid uas tso cai rau 30-50%.

Phau Ntawv Qhia rau Kev Tswj Cov Acid Acid Impurity hauv Sodium Acetate Heater

Qhov siab tshaj plaws tso cai ntau ntawm acetic acid rau Qib 2 titanium cov cua sov hauv 50% sodium acetate ntawm 90℃tau qhia hauv cov lus hauv qab no rau ntau lub neej kev pabcuam thiab sib txawv tso cai blistering.

Desired Service Life (years) Maximum Allowable Acetic Acid (ppmExpected pH range Blistering potentialRecommended Action >5 <300 >6.0 Tsis Muaj Tsis Muaj 3–5 300–500 5.0–6.0 Kev soj ntsuam qis Peb lub hlis twg 1–3 500–800 4.5–5.0 Nruab nrabNeutralize nrog sodium hydroxide<1 800-1000 4.0-4.5 High Purify solution
Not acceptable >1,000 <4.0 Severe Change solution
Engineering Beyond Acetic Acid Control

Qib titanium yuav cuam tshuam rau kev tiv thaiv blistering. Qib 7 (palladium stabilized) yog 3 mus rau 5 zaug siab dua rau acetic acid vim palladium catalyzes hydrogen recombination, yog li txo cov hydrogen mus rau hauv cov hlau. Qib 12 muab kev txhim kho nruab nrab. Blistering tsis tiv thaiv los ntawm phab ntsa tuab, tab sis cov phab ntsa tuab tuaj yeem siv cov hlwv ntau dua ua ntej xau. Tshawb xyuas pH ntawm cov tshuaj tsis tu ncua. Yog tias pH qis dua 7, ntxiv sodium hydroxide kom nce pH. acetic acid pib permissible. Nitrogen daim pam kom tshem tawm cov pa oxygen. Ib qho oxidant, xws li sodium nitrite (100 ppm), ntxiv, nce qhov pib, txhawb kev txo qis oxygen tshaj hydrogen evolution.

Txhim kho qhov zoo - Qhia meej meej

Nyob rau hauv cov ntaub ntawv ntawm Qib 2 titanium rhaub cua sov 50% sodium acetate ntawm 90C, kom muaj kev nyab xeeb ntawm qis dua 500 ppm blistering pib, acetic acid impurity yuav tsum tau khaws cia qis dua 300 ppm. Ntsuas pH ib zaug ib lub lim tiam. Yog tias nws poob qis dua 7, ntxiv 0.1 feem pua ​​sodium hydroxide kom nce pH. Qhov twg acetic acid ntau dua 500 ppm, siv Qib 7 titanium los yog ntxiv cov oxidant xws li 100 ppm sodium nitrite. Tshawb xyuas cov hlwv ntawm lub tshuab cua sov thaum ua haujlwm txhua 3 lub hlis. Yog tias pom, neutralize cov tshuaj thiab hloov lub rhaub. Tus kws ua haujlwm yuav tsum khaws cov acetic acid impurity qis dua 500 ppm los tiv thaiv hydrogen blistering ntawm Qib 2 titanium cua sov siv hauv kev pabcuam sodium acetate.