Thaum lub titanium Sheath rhaub tau nruab kab rov tav nyob rau hauv 25% Sodium Chloride Brine ntawm 95 degree, Yuav Ua Li Cas Lub Cev Qhov Ncauj Raws Li Kev Txhawb PTFE (0.1 hli vs . 0.5 hli) Hloov Lub Sijhawm rau Crevice Corrosion ntawm Titanium?

Lub titanium sheath rhaub txhawb rau PTFE brackets nyob rau hauv 25% ntsev chloride brine ntawm 95℃qhia crevice corrosion ntawm qhov chaw tiv tauj. Qhov hnyav nyob ntawm qhov sib txawv ntawm qhov crevice. Ntawm qhov sib txawv nruj ntawm 0.1 hli, brine raug cais tawm thiab tsis muaj kev cuam tshuam corrosion tsis pib. Nws muaj 0.5 hli qhov chaw uas cov brine zaum thiab nkag mus. Chlorides mloog zoo rau 50, 000 - 100,000 ppm Oxygen yog depleted pH tee Crevice corrosion pib ntawm 200 mus rau 500 teev thiab pib ntawm tus nqi ntawm 0.5 mus rau 1.5 hli txhua xyoo.

Mechanism ntawm Crevice Corrosion raws li kev ua haujlwm ntawm qhov sib txawv

Capillary rog hauv qhov sib txawv me me (<0.2 mm) impede electrolyte entry. Moderate gap (0.2-0.5 mm) electrolyte penetrates but does not circulate. Oxygen is used up, chlorides become concentrated and the crevice turns acidic. For titanium in hot brine, the critical gap for crevice initiation is in the range of 0.1-0.3 mm. If the distance is >0.5 hli, ces ncig yog txaus kom tsis txhob hnyav concentration.

Quantitative Crevice Initiation Time vs. Gap Size

Qib 2 titanium tau sim hauv 25% NaCl ntawm 95℃raws li kev txhawb nqa PTFE nrog cov txiaj ntsig hauv qab no. Ntawm qhov sib txawv<0.1 mm the initiation time of a crevice is greater than 10,000 hours and no corrosion occurs. The initiation time is 1,000-3,000 hours at a gap of 0.1-0.2 mm, and some minor pitting may occur. The initiation time is 300-800 hours with a gap of 0.2-0.3 mm. Crevice corrosion is moderate. At a gap 0.3-0.5 mm start time is 150-400 hours and severe crevice corrosion. Initiation period, 500-1500 hours at a gap >0.5 hli. Tawm tsam, tsis tshua muaj hnyav (kho kom zoo dua vim kev ncig).

Crevice Gap Design Guide

Crevice Gap (mm) Risk ntawm Crevice Corrosion Pib Lub Sijhawm (teev) Pom Zoo Txhawb Tsim<0.1 None >10,000 Ideal (nias haum)
0.1-0.2 Tsawg 1,000-3,000 Txais
0.2-0.3 Moderate 300-800 Avoid 0.3-0.5 High 150-400 Avoid >0.5 Tsawg (kev ncig) 500-1,500 Txais tau nrog cov kua dej
Tsim ib qho kev qhia tshwj xeeb

Tsim PTFE txhawb nqa nrog nruj haum (<0.1 mm gap) or with an open gap >0.5 hli tso cai rau kev ncig rau titanium rhaub hauv 25% NaCl ntawm 95 degree. Tsis txhob muaj qhov sib txawv ntawm 0.2-0.5mm. Tus engineer tswj lub crevice geometry los tiv thaiv crevice corrosion.