Yuav Ua Li Cas Qhov Nto Hlau Los Ntawm Kev Ua Haujlwm (10 Ng / Cm² Vs . 100 Ng / Cm²) Ntawm Titanium Sheath Heater Hloov Qhov Qhib -Circuit Potential Drift Thiab Lub Sijhawm Los Pib Crevice Corrosion Hauv 1% NaCl Ntawm 60℃?
Tso lus
Surface iron contamination on titanium heaters creates local galvanic cells. Iron particles are more noble than titanium in chloride solutions. At low contamination (10 ng/cm²), open-circuit potential (OCP) drifts slowly (-0.05 V over 500 hours) and crevice corrosion initiates after >2,000 teev. Thaum muaj kab mob siab (100 ng / cm²), OCP drifts sai (-0.2 V tshaj 100 teev) thiab crevice corrosion pib hauv 200-500 teev.
Quantitative OCP Drift thiab Crevice Initiation
Hauv 1% NaCl ntawm 60℃rau Qib 2 titanium:
| Hlau Contamination (ng / cm²) | OCP Drift (V vs. Ag/AgCl) tom qab 100h | Crevice Initiation Sijhawm (teev) | Max qhov tob tom qab 1,000h (µm) |
|---|---|---|---|
| 0 (huv) | 0-0.02 Nws | >5,000 | 0 |
| 10 | -0.02 - 0.05 Nws | 2,000–4,000 | 10–30 |
| 25 | -0.05 - 0.10 | 1,000–2,000 | 20–60 |
| 50 | -0.10 - 0.15 | 500–1,000 | 50–100 |
| 100 | -0.15 - 0.25 Nws | 200–500 | 100–200 |
| 200 | -0.25 - 0.40 Nws | 100–200 | 150–300 |
Cov nyhuv ntawm Chloride Concentration rau Hlau Aggressiveness
| NaCl Concentration (%) | Hlau 50 ng / cm² - Pib Lub Sijhawm (teev) | Clean Surface Initiation (teev) |
|---|---|---|
| 0.5 | 1,000–2,000 | >5,000 |
| 1.0 | 500–1,000 | >5,000 |
| 3.0 | 200–500 | 2,000–4,000 |
| 5.0 | 100–300 | 1,000–2,000 |
Phau Ntawv Qhia Txog Kev Tu thiab Kev Tshawb Fawb
| Qib sib kis (ng / cm²) | Pom zoo txoj kev ntxuav | OCP tom qab ntxuav (V vs. Ag / AgCl) |
|---|---|---|
| <10 (clean) | Tsis muaj | -0.05 - 0.10 |
| 10–50 | Alkaline degrease + kua qaub | -0.05 - 0.10 |
| 50–100 | Nitric acid (20%, 50 degree, 10 min) | -0.05 - 0.10 |
| >100 | Nitric{0}}HF pickle + electropolish | -0.05 - 0.10 |
Kev pom zoo engineering
Rau titanium heaters nyob rau hauv cov kev pab cuam chloride, qhia kom meej qhov siab tshaj plaws hlau paug ntawm 10 ng / cm². Ntxuav nrog 20% nitric acid ntawm 50℃rau 10 feeb. Ntsuas OCP tom qab ntxuav; Yog tias OCP tsis zoo dua li -0.10 V vs Ag / AgCl, rov ua dua. Los ntawm kev tswj cov hlau nto, tus kws ua haujlwm tiv thaiv OCP drift thiab crevice corrosion.
