Pitting corrosion: ua rau. Txoj kev tiv thaiv cov hlau los ntawm corrosion

2024 Tus sau: Howard Calhoun | [email protected]. Kawg hloov kho: 2023-12-17 10:28

Corrosion yog kev puas tsuaj ntawm cov ntaub ntawv saum npoo raws li kev ua haujlwm dhau los ntawm cov txheej txheem redox. Kev puas tsuaj ntawm cov khaubncaws sab nraud povtseg ntawm cov khoom ua rau txo qis zog, hluav taws xob conductivity, nce brittleness thiab inhibition ntawm lwm yam khoom ntawm cov hlau.

Thaum lub sijhawm ua haujlwm ntawm cov khoom siv hlau, lawv raug rau ntau hom kev puas tsuaj, ntawm cov pitting corrosion stands. Nws yog qhov txaus ntshai tshaj plaws thiab tsis paub txog.

Nyob zoo ib tsoom niam txiv kwv tij neej tsas sawv daws

Ntawm qhov chaw ntawm cov khoom hlau, koj tuaj yeem pom muaj kev nyuaj siab me me, cov xim xim av lossis xim av. Cov kws tshawb fawb hu cov ntsiab lus pitting, thiab cov txheej txheem ntawm lawv cov tsos yog hu ua pitting corrosion. Nws tshwm sim nyob rau saum npoo ntawm cov ntaub ntawv uas tuaj rau hauv kev sib cuag nrog dej hiav txwv, kev daws teeb meem ntawm ntau yam ntsev, tshuaj lom neeg ib puag ncig thiab pom lwm yam tsis zoo.

Pitting corrosion cuam tshuam tsuas yog cov hlau tsis muaj zog thiab cov hlau, nws txhim kho feem ntau hauv cov txheej tiv thaiv corrosion los yog nyob rau hauv qhov chaw ntawm ntau yam tsis xws luag. "Point ulcers" tuaj yeem cuam tshuam nrog kev ua haujlwm ntawm ntau yamcov khoom: los ntawm nyias daim nyias nyias thiab microcircuits rau tuab-walled aggregates. Tsis tas li ntawd, lawv cov tsos ua rau muaj kev txhim kho corrosion, uas txo qis cov yam ntxwv ntawm cov khoom siv.

Metal destruction scheme

Txhawm rau qhib pitting corrosion, muaj ob lub reagents yog tsim nyog - activators thiab passivators. Anions ntawm chlorine, bromine, iodine feem ntau ua raws li cov activators - lawv pom nyob rau hauv feem ntau qhov chaw uas cov khoom hlau ua haujlwm. Lawv yog adsorbed rau saum npoo hlau thiab tsim cov soluble complexes nrog nws cov khoom.

Dej lossis ib pawg hydroxyl feem ntau ua raws li tus neeg mob. Cov txheej txheem kev puas tsuaj nws tus kheej ua raws li cov txheej txheem hauv qab no:

1. Activator ions yog adsorbed rau ntawm qhov chaw tiv thaiv (oxide) zaj duab xis.
2. Muaj txheej txheem hloov cov pa oxygen ions nrog cov txheej txheem activator ions.
3. Ib qho loj ntawm cov ions soluble tsim, ua rau cov yeeb yaj kiab tawg.

Raws li qhov tshwm sim ntawm qhov no, qhov sib txawv muaj peev xwm tshwm sim ntawm qhov chaw ntawm cov khoom siv, uas ua rau pom cov dej ntws hauv zos, thiab cov txheej txheem anode hnyav tau qhib. Nyob rau tib lub sijhawm, activating ions txav mus rau qhov chaw ntawm kev puas tsuaj, vim qhov pitting corrosion nce.

Ntau yam ntawm pitting corrosion

Hom pitting corrosion txawv nyob ntawm qhov chaw ib puag ncig, feem ntau yog kub, acidity, tshuaj muaj pes tsawg leeg ntawm cov khoom. Raws li kev cuam tshuam ntawm cov xwm txheej no, cov duab hloov pauv,qhov loj ntawm lub pits thiab lawv qhov chaw. Yog li, raws li qhov loj me, taw tes kev puas tsuaj yog qhov txawv:

• microscopic - dot loj dua 0.1 hli;
• tsis tu ncua - txoj kab uas hla ntawm qhov sib txawv ntawm 0.1 txog 1 hli;
• ulcerative thaum formations ntau tshaj 1 mm inch.

Nyob ntawm qhov chaw, pitting corrosion tuaj yeem qhib lossis kaw. Nyob rau hauv thawj rooj plaub, nws yuav luag tsis yooj yim sua kom nrhiav tau ib qho kev puas tsuaj - nws yog ib qho tsim nyog yuav tau siv cov cuab yeej tshwj xeeb. Hom corrosion no feem ntau ua rau tawg.

Tshuaj xeb pom ntawm qhov muag liab qab. Feem ntau pittings merge rau hauv ib qho kev tsim. Hauv qhov no, kev puas tsuaj ntawm cov khoom siv tsis tshwm sim hauv qhov tob, tab sis nyob rau hauv dav, uas ua rau muaj qhov tsis xws luag ntawm thaj chaw loj.

Shape of pits

Cov duab ntawm lub pitting yog nyob ntawm cov voids hauv cov siv lead ua lattice, uas yog tsim nyob rau hauv thawj theem ntawm cov txheej txheem corrosion. Feem ntau cov qauv ntawm cov duab tsis sib xws - lawv tshwm sim rau ntawm qhov chaw ntawm stainless, qis-alloy thiab carbon steels, aluminium, chromium, npib tsib xee alloys, hlau.

Hemispherical ulcers yog tsim los ntawm isotropic dissolution. Cov txheej txheem no zoo ib yam li electropolishing. Qhov no qhia txog qhov ci hauv qab ntawm lub semicircular recesses. Qhov cuam tshuam rau kev puas tsuaj ntau tshaj plaws yog titanium, aluminium, npib tsib xee thiab cob alt khoom, nrog rau cov qauv tantalum. Kwv yees li qhov zoo li qubpitting corrosion ntawm stainless hlau.

Dhau li ntawm, pittings tuaj yeem ua tau ntau yam thiab ntsej muag. Cov "ulcers" ntawm hom tom kawg feem ntau ua ke nrog ib leeg, uas ua rau cov pob txha loj hemispherical.

Yog vim li cas thiaj pom

Qhov laj thawj tseem ceeb ntawm pitting corrosion yog kev ua txhaum ntawm cov cuab yeej tsim khoom thiab kev cuam tshuam rau cov khoom siv. Raws li qhov tshwm sim ntawm kev ua txhaum ntawm kev siv tshuab casting, ntau yam microinclusions tshwm sim hauv cov hlau, uas ua txhaum nws cov qauv. Qhov feem ntau suav nrog tuaj yeem hu ua zeb nplai.

Vim muaj kev cuam tshuam rau txhua yam, feem ntau pitting corrosion pib tsim rau ntawm cov khoom. Yog vim li cas rau qhov no dag nyob rau hauv kev puas tsuaj ntawm lub Upper tiv thaiv zaj duab xis, kev ua txhaum ntawm lub internal qauv, thiab tshwm sim ntawm grain ciam teb rau saum npoo. Qhov feem ntau tshwm sim ua kom cov txheej txheem tuaj yeem hu ua qhov cuam tshuam zoo, uas ua rau cov tsos ntawm microcracks.

Pitting corrosion ntawm cov hlau tsim sai dua ntawm qhov chaw ntxhib, nrog rau kev cuam tshuam ntawm qhov chaw hnyav - dej hiav txwv, kua qaub.

Txoj kev tiv thaiv hlau los ntawm pitting corrosion

Tiv thaiv cov khoom hlau los ntawm pitting corrosion, peb txoj hauv kev tseem ceeb yog siv:

1. Kev ua kua ntawm kaw kaw siv cov kev daws teeb meem ntawm alkaline compounds, sulfates, chromates.
2. Kev taw qhia ntawm cov khoom siv nrog kev ua haujlwm siab rau pitting xeb rau hauv cov khoom siv - molybdenum,chromium, silicon.
3. Siv cathode thiab anode thev naus laus zis los tsim cov txheej txheem tiv thaiv.

Txhua txoj kev qhia txog kev tiv thaiv cov hlau los ntawm corrosion tsuas yog siv rau hauv kev tsim khoom, vim lawv xav tau cov cuab yeej siv siab thiab kev nqis peev loj. Nyob rau hauv lub neej txhua hnub, nws yog tsis yooj yim sua kom tshem tawm tag nrho cov kev pheej hmoo ntawm pitting. Nws tsuas yog ua tau kom tsis muaj zog ntawm kev ua tsis zoo los ntawm:

• tiv thaiv corrosion;
• txhim kho kev ua haujlwm ntawm cov khoom;
• txo qib ntawm acidity ntawm ib puag ncig uas cov khoom nkag mus rau hauv kev sib cuag.

Tab sis txoj kev ua tau zoo tshaj plaws thiab pheej yig tshaj yog kev txhuam kom zoo: los ntawm kev txo qhov roughness ntawm qhov chaw, koj ib txhij nce nws cov kev tiv thaiv corrosion. Tab sis kom tau txais txiaj ntsig zoo tshaj plaws, nws yog qhov zoo dua los siv txhua txoj hauv kev los tiv thaiv cov hlau los ntawm corrosion tib lub sijhawm.