Rau Titanium Immersion rhaub hauv 5% Sodium Persulfate Solution ntawm 50 degree, Vim li cas Persulfate Ion tsis Passivate titanium txawm tias nws yog ib qho muaj zog Oxidizer, thiab Es tsis txhob ua rau Transpassive Dissolution?

Na 2 S 2 O 8 ) is a greater oxidiser ( E o = 2.01 V for S 2 O 8 2 - / SO 4 2 - ) than nitric acid . However, on titanium persulfate induces transpassive dissolution, not stable passivation. At 50°C the high oxidation potential moves the titanium surface into the transpassive area (>1.8 V vs. SCE) qhov twg cov zaj duab xis passive tawg thiab titanium dissolves li Ti4+ ntawm tus nqi ntawm 0.2-0.5 hli ib xyoo.

Corrosion tus nqi vs persulfate concentration (quantitative)

500 teev ntawm 50℃hauv Na2S2O8:

Persulfate Concentration (%) Corrosion Rate (mm/xyoo) Surface potential (V vs. SCE) Mechanism 0 0.005–0.010 0.2–0.5Passive 1 0.05-0.12 1.2-1.5 Mixed
3 0.12–0.25 1.5–1.7 Pib ntawm transpassive
5 0.20–0.40 1.7–1.9 Transpassive 10 0.35–0.60 1.8–2.0 Muaj zog Transpassive Temperature Effect rau Transpassive Transition

Kub (degree) 5% Persulfate – Corrosion Rate (mm/xyoo) Mechanism 25 0.10–0.20 Transpassive 40 0.15–0.30Transpassive 50 0.20–0.40Transpassive 60 0.30–0.60 Mob hnyav
Pom zoo rau Engineering

Titanium tsis pom zoo rau cov tshuaj persulfate vim yog transpassive dissolution. Siv PTFE coated cua sov los yog Tantalum. Titanium yuav tsum tau siv rau qhov kub thiab txias<30°C and persulfate should be limited to <2% if it must be used. The engineer can choose the right materials by knowing the transpassive behaviour of the persulfate.