Hauv Titanium Immersion Rhaub Siv los Preheat 35% Methanol / Dej Sib xyaw ntawm 65 degree, Vim Li Cas Ntxiv 0.5% Sodium Hydroxide Hloov Cov Txheej Txheem Corrosion los ntawm Uniform Thinning rau Pitting?

Qib 2 titanium thins uniformly ntawm 0.02-0.05 hli / xyoo hauv 35% methanol / dej ua ke ntawm 65 degree. Lub pH yog nce mus rau 10-11 nrog ntxiv ntawm 0.5% sodium hydroxide (NaOH). Ntawm qhov pH siab no cov titanium passive zaj duab xis tsis tshua muaj kev ruaj ntseg hauv methanol vim yog kev loj hlob ntawm soluble titanates. Corrosion mechanism hloov los ntawm uniform mus rau hauv zos pitting. Qhov tob ntawm qhov tob yog 0.2 - 0.8 hli / xyoo, 10 mus rau 20 npaug sai dua li cov txheej nyias nyias. Qhov kev hloov no yog ntaus nqi rau cov pH siab uas haum rau TiO 2 dissolution los tsim titanate ions (TiO 3 2-) nyob rau hauv lub xub ntiag ntawm methanol.

Mechanism ntawm Kev Hloov ntawm Uniform rau Pitting Corrosion Induced los ntawm pH

Cov zaj duab xis passive ntawm titanium yog ruaj khov hauv methanol / dej sib tov ntawm nruab nrab pH (6-7). Zaj duab xis maj mam thiab sib npaug. Thaum pH siab (10–11) hydroxyl ions react nrog TiO2: TiO2 + 2OH− → TiO3 2− + H2O Cov titanate ions yog soluble hauv methanol / dej ua ke uas ua rau cov yeeb yaj kiab thinning. Txawm li cas los xij, qhov kev ua phem tsis sib xws vim kev tawg ntawm cov zaj duab xis passive ntawm qhov chaw tsis muaj zog xws li cov ciam teb lossis cov khoom sib txuas. Thaum lub qhov pib pib, qhov pH siab hauv lub qhov yog khaws cia thiab lub qhov dej loj hlob sai.

Quantitative Corrosion Rate thiab Mechanism Versus NaOH Concentration

Kev ntsuas ntsuas rau Qib 2 titanium dhau lub sijhawm 500 teev ntawm 65℃hauv 35% methanol / dej nrog ntau qhov sib txawv ntawm NaOH tau qhia cov hauv qab no. Ntawm 0% NaOH (pH 6–7) corrosion tus nqi yog 0.02–0.05 mm / xyoo, mechanism uniform thiab pitting ceev 0 pits / cm 2 . Tus nqi ntawm 0.1% NaOH (pH 9) yog 0.03–0.06 mm/xyoo, lub mechanism yog tov thiab pitting 1 cm dens. Tus nqi yog 0.05-0.12 hli / xyoo ntawm 0.3% NaOH (pH 10), cov txheej txheem sib xyaw thiab pitting ceev yog 5 txog 20 pits / cm2. Qhov tseem ceeb tshaj plaws yog pom ntawm 0.5% NaOH (pH 11) nrog tus nqi ntawm 0.10-0.25 mm / xyoo, pitting raws li ib tug mechanism thiab pitting ceev ntawm 20-80 pits / cm². Hauv 1.0% NaOH (pH 12) tus nqi yog 0.20 txog 0.50 mm / xyoo, lub tshuab yog qhov hnyav pitting, thiab pitting ceev yog 50 txog 150 pits / cm².

Cov nyhuv ntawm Methanol Concentration ntawm kev hloov ntawm pH

Kev hloov pauv los ntawm kev sib txuam mus rau pitting tau pom ntawm ntau yam pH qhov tseem ceeb nyob ntawm seb muaj pes tsawg tus methanol. Hauv dej ntshiab (0% methanol) nrog 0.5% NaOH (pH 11) cov txheej txheem yog sib xws nrog tus nqi corrosion ntawm 0.08-0.15 hli hauv ib xyoos uas tsis muaj pitting. Hauv 20% methanol nrog 0.5% NaOH cov txheej txheem ua ke thiab pitting ceev yog 5-15 pits / cm2. Lub tshuab yog pitting hauv 35% methanol nrog 0.5% NaOH thiab qhov ceev yog 20-80 pits / cm2. Hauv 50% methanol nrog 0.5% NaOH, lub tshuab yog pitting nrog qhov ceev ntawm 30-100 pits / cm². Lub tshuab yog qhov hnyav heev nrog ntau dua 50 pits / cm² hauv 70% methanol nrog 0.5% NaOH. Cov ntsiab lus methanol siab dua ua rau ntau pitting ntawm pH muab.

Methanol/Dej Heaters pH Control

Cov lus hauv qab no muaj cov lus qhia rau siab tshaj pH kom muaj kev sib haum xeeb rau Qib 2 thiab Qib 7 titanium rhaub hauv 35% methanol / dej ntawm 65 degree.

Qhov xav tau Mechanism Maximum pH rau Qib 2 Qhov siab tshaj pH rau Qib 7 Pom zoo NaOH Concentration (%) Xav 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 (marginal) 9–10 10–11 0.1–0.3 0.05–0.12
Avoid pitting >10 >11 >0.3 >0.12
Engineering dhau los ntawm pH

Qib ntawm titanium cuam tshuam rau kev hloov pauv pH. Qib 7 (palladium{2}}stabilized) txav cov khaub ncaws mus rau pitting hloov mus rau pH 10-11 tso cai rau kev nyab xeeb ntawm 0.5% NaOH (pH 11) hauv 35% methanol. Muaj qee qhov kev txhim kho nyob rau qib 12. Phab ntsa tuab tso cai rau kev nkag mus rau qhov tob. Phab ntsa ntawm 2.0 hli nrog pitting ntawm 0.2 hli ib xyoo yuav kav 10 xyoo. Qhov kev pheej hmoo ntawm pitting yog txo los ntawm kev ntxiv dej rau methanol / dej sib tov; ntawm 50% dej (50% methanol) hloov pH yog 10.5. Lub xub ntiag ntawm chlorides hauv cov tshuaj txo cov kev hloov pauv pH los ntawm 1-2 units.

Ua ib qho Specification qhia

Titanium immersion rhaub hauv 35% methanol / dej ntawm 65 degree, tsis txhob ntxiv NaOH siab tshaj 0.1% rau Qib 2 lossis siab dua 0.3% rau Qib 7. Yog tias pH raug txiav txim los ntawm cov txheej txheem vim li cas alkaline, siv Qib 7 titanium thiab khaws pH hauv qab no 11. Cov cua sov uas twb muaj lawm yuav tsum tau kuaj xyuas pH5%. xim penetrant. Yog tias pom pitting, hloov lub rhaub thiab txo pH. Thaum lub sijhawm ua haujlwm, sim pH txhua lub lim tiam thiab yog tias pH yog> 9 (Qib 2) lossis> 10 (Qib 7), siv acetic acid kom txo pH. Tus kws tshaj lij tswj hwm pH hauv qab qhov hloov pauv tseem ceeb los tiv thaiv qhov kev hloov pauv los ntawm cov txheej txheem thinning kom nrawm pitting hauv methanol / dej sib tov.