Rau Titanium Tshav Kub Kub Siv los rov ua kom sov 30% Sodium Thiocyanate Solution ntawm 80 degree, Thiocyanate Anion Yuav Ua Li Cas Thiaj Li Tiv Thaiv Chloride-Induced Pitting?

Nws tau pom tias thiocyanate anions (SCN{0}}) muaj zog adsorb ntawm titanium nto hauv 30% sodium thiocyanate (NaSCN) ntawm 80℃los tsim ib qho kev tiv thaiv. Cl- ions sib tw nrog SCN- rau qhov chaw adsorption ntawm qhov chaw. SCN- muaj adsorption affinity ntau dua li Cl- thiab, yog li ntawd, tshem chloride los ntawm qhov chaw thiab tiv thaiv chloride -induced pitting. Qhov inhibition efficiency yog nce los ntawm qhov concentration ntawm SCN- . Pitting yog tag nrho suppressed thaum molar ratio SCN- / Cl- siab tshaj 2. Cov txheej tiv thaiv yog titanium-thiocyanate complex uas tiv thaiv kev nkag ntawm chloride rau cov hlau nto.

Mechanism ntawm Competitive Adsorption thiab Pitting Inhibition

Thiocyanate yog lub hauv paus mos, uas sib koom ua ke thiab muaj zog rau saum npoo atoms ntawm titanium. Chloride yog lub hauv paus nyuaj thiab tsim cov kev sib txuas tsis muaj zog electrostatic. Hauv cov kev daws teeb meem sib xyaw SCN⁻ nyiam adsorbs thiab thaiv qhov chaw saum npoo uas yuav muaj cov tshuaj chloride. Cov txheej SCN tso cia kuj hloov kho cov nqi saum npoo thiab rov ua cov tshuaj chloride ions. Qhov inhibition ua raws li Langmuir isotherm θ  K [SCN ] 1  K [SCN ] (1) qhov twg θ yog qhov chaw npog thiab K yog qhov adsorption equilibrium tas li.

Quantitative pitting inhibition raws li kev ua haujlwm ntawm SCN - / Cl - piv

Cov nram qab no tau tsim los rau Qib 2 titanium los ntawm kev tswj xyuas hauv 1,000 ppm Cl- kev daws teeb meem ntawm 80℃thiab ntau yam SCN- concentrations rau 500 teev. SCN - /Cl - molar ratio 0 (0 ppm SCN - ) Pitting ceev 50-150 pits/cm 2 Qhov siab tshaj plaws qhov tob 200-500 microns Qhov pitting ceev ntawm qhov ratio ntawm 0.5 (0.5 ppm) 10-30 pits/cm2 thiab qhov tob yog 50-100 µm. Pitting ntom yog 2-10 pits / cm 2 thiab qhov tob yog 10-30 µm ntawm qhov sib piv ntawm 1.0 (1,000 ppm SCN -) 2.0 piv (2,000 ppm SCN-) muaj pitting ntom ntawm 0 pit / cm2 thiab qhov tob ntawm kev tiv thaiv 0µm). Ntawm qhov piv ntawm 5.0 (5000 ppm SCN -), pitting ceev yog 0 thiab qhov tob qhov tob yog 0.

Qhov ntsuas tseem ceeb raws li Kev Ua Haujlwm ntawm Kub thiab Chloride Concentration

Raws li qhov ntsuas kub nce qhov tsawg kawg nkaus ntawm SCN-/Cl- rau kev tiv thaiv tag nrho nce. Ntawm 40℃qhov piv yog 0.8. Ntawm 60℃qhov piv yog 1.2. Qhov piv yog 2.0 ntawm 80 degree. Qhov piv ntawm 100℃yog 3.0. Qhov yuav tsum tau piv kuj nce nrog chloride concentration. Ntawm 500 ppm Cl⁻ qhov piv yog 1.5, ntawm 1,000 ppm Cl⁻ qhov piv yog 2.0 thiab ntawm 5,000 ppm Cl⁻ qhov piv yog 3.0.

Thiocyanate: Qhov zais cia rau Chloride Pitting Tiv Thaiv

Cov lus hauv qab no muab kev taw qhia ntawm SCN⁻ concentration kom tsis txhob muaj cov tshuaj chloride-induced pitting ntawm Qib 2 titanium rhaub ua haujlwm ntawm 80℃.

Concentration ntawm chloride, ppm Yam tsawg kawg nkaus SCN- kom tiav kev tiv thaiv, ppmSCN⁻ (ppm) pom zooSCN-/Cl- Molar Ratio 100 200 300 2.0 250 500 750 2.0 500 1,000 1,500 2.0 1,000 2,000 3,000 2.0 2,000 4,000 6,000 2.0 5,{11}},000 15,000 2.0 Engineering tshaj thiocyanate concentration tswj

Qib ntawm titanium dictates SCN⁻ concentration tsim nyog. Qib 7 (palladium stabilized) muaj qhov xav tau qis dua (1.0-1.5 SCN-/Cl- piv ntawm 80 C) vim nws qhov chaw zoo dua. Phab ntsa thickness muab lub qhov nkag mus rau qhov tso cai yog tias inhibition tsis tiav. Kev ruaj ntseg ntawm SCN - yog pH nyob ntawm. Ntawm pH <4, SCN- hydrolyzes rau HCN thiab poob. SCN⁻ ruaj khov ntawm pH > 10. Oxidizing tshuaj (xws li, Fe³⁺) tuaj yeem oxidize SCN⁻ rau sulfate, yog li txo qis inhibition.

Paub Specification

Rau titanium tshav kub pas nrig hauv 30% sodium thiocyanate ntawm 80℃nrog cov tshuaj chloride paug, cov molar ratio SCN-/Cl- yuav tsum tau khaws cia siab tshaj 2.0 kom tsis txhob pitting. Yog tias cov ntsiab lus chloride tsis paub meej, siv SCN- ntawm 5,000 ppm (0.5%) raws li cov tshuaj tiv thaiv dav dav. titration txhua lub lim tiam los xyuas SCN- concentration. Yog tias qhov sib piv poob qis dua 2.0, ntxiv sodium thiocyanate. Rau cov cua sov uas twb muaj lawm nrog pitting, nce SCN⁻ concentration mus txog 10,000 ppm rau ib lub sij hawm luv luv kom repassivate saum npoo. Tus kws tshaj lij siv thiocyanate los ua ib qho kev sib tw adsorbate los tiv thaiv titanium cua sov tiv thaiv chloride pitting.