Hauv Titanium Tube Bundle Heater rau 20% Ammonium Nitrate Solution ntawm 80 degree, Lub pH (4.5 vs . 6.5) Yuav ua li cas hloov cov Passivation tam sim no ntom thiab qhov pheej hmoo ntawm kev ntxhov siab Corrosion tawg?

Cov pH ntawm cov tshuaj (20%) muaj kev cuam tshuam zoo rau kev coj tus cwj pwm passivation ntawm titanium hauv ammonium nitrate (NH4NO3) ntawm 80 degree. Ntawm pH 6.5 (ze rau nruab nrab), cov zaj duab xis passive yog ruaj khov nrog passivation tam sim no ntom ntawm 0.05-0.1 µA / cm² thiab tsawg SCC kev pheej hmoo. Ntawm pH 4.5 (acidic los ntawm hydrolysis) passivation tam sim no ceev nce mus rau 0.5 - 2 µA / cm2 thiab qhov tshwm sim ntawm kev ntxhov siab corrosion cracking (SCC) ntau zuj zus vim yog kev ua phem ntawm nitrate ion ntawm qis pH.

Quantitative Passivation Current Versus pH

Rau Titanium qib 2 hauv 20% NH4NO3 ntawm 80 ° C:

pH Passivation Current Density (µA/cm2) SCC Initiation Time (teev) SCC Risk
6.5 0.05-0.10 >5,000 Low 6.0 0.08-0.15 3,000-5,000 Low-Moderate 5.5 0.15-0.30 1,000-3,000 Nruab Nrab 5.0 0.30-0.70 500-1,500 Siab 4.5 0.50-1.50 200-800Severity 4.0 1.0–3.0 100–400Zoo heev, tab sis
Kev sib cuam tshuam ntawm chloride thiab nitrate

pH Chloride (ppm) SCC RiskSuggested Qib 6.5 0 Qib Qib qis 2 6.5 100 Qib Nruab Nrab 2 5.5 0 Qib Nruab Nrab 2 5.5 100 Qib Siab 7 4.5 0 Qib Siab 7 4.5 100 Qib hnyav 7 + Kev cais pH Tswj Kev Qhia

Operating pH Recommended actionExpected SCC Free Life ( Grade 2)6.0 None >10 xyoo
5.5–6.0 Kev soj ntsuam pH txhua lub lim tiam 5–10 xyoo
5.0-5.5 Kho pH siv NH4OH 3-5 xyoo
4.5–5.0 Siv Ti Qib 7 5–8 xyoo (Ti Qib 7)
<4.5 Redesigning process <2 years
Kev pom zoo ntawm Engineering

Rau kev pabcuam ammonium nitrate khaws pH> 5.5 rau Qib 2 lossis> 5.0 rau Qib 7. Ntxiv ammonium hydroxide rau neutralize acidity. Tus kws tshaj lij tswj hwm pH kom txo qis kev ua haujlwm tam sim no kom tsawg thiab txo qis kev ntxhov siab corrosion tawg.