Corrosion vs Rusting
Corrosion thiab xeb yog ob txheej txheem tshuaj, uas ua rau cov khoom tawg.
Corrosion
Thaum cov ntaub ntawv cuam tshuam nrog ib puag ncig sab nraud, dhau sijhawm, nws cov qauv yuav tsis zoo, thiab tawg ua me me. Thaum kawg, nws tuaj yeem tawg mus rau qib atomic. Qhov no yog hu ua corrosion. Feem ntau qhov no tshwm sim rau cov hlau. Thaum raug rau ib puag ncig sab nraud, cov hlau yuav raug oxidation cov tshuaj tiv thaiv nrog oxygen hauv cov huab cua. Lwm yam tshaj li hlau, cov ntaub ntawv zoo li polymers, ceramics kuj tuaj yeem raug kev puas tsuaj. Txawm li cas los xij, hauv qhov no, nws yog hu ua degradation. Cov yam ntxwv sab nraud uas ua rau cov hlau corrode yog dej, acids, bases, ntsev, roj, thiab lwm yam khoom thiab kua tshuaj. Tsis tas li ntawd, cov hlau corrode thaum raug cov ntaub ntawv gaseous xws li kua qaub vapors, formaldehyde gas, ammonia roj, thiab leej faj uas muaj gases. Lub hauv paus ntawm cov txheej txheem corrosion yog cov tshuaj tiv thaiv electrochemical. Nyob rau hauv cov hlau qhov twg corrosion tshwm sim, ib tug cathodic thiab anodic tshuaj tiv thaiv tshwm sim. Thaum cov hlau atoms raug dej, lawv muab electrons rau oxygen molecules thiab tsim cov hlau ions zoo. Qhov no yog cov tshuaj tiv thaiv anodic. Cov khoom siv hluav taws xob tau siv los ntawm cov tshuaj tiv thaiv cathodic. Ob qhov chaw uas cov tshuaj tiv thaiv cathodic thiab cov tshuaj tiv thaiv anodic tshwm sim tuaj yeem nyob ze rau ib leeg lossis nyob deb nyob ntawm qhov xwm txheej. Qee cov ntaub ntawv muaj kev tiv thaiv corrosion, tab sis qee qhov muaj kev tiv thaiv corrosion. Txawm li cas los xij, corrosion tuaj yeem tiv thaiv los ntawm qee txoj kev. Txheej yog ib txoj hauv kev los tiv thaiv cov ntaub ntawv los ntawm corrosion. Qhov no suav nrog kev pleev xim, plating, thov enamel rau saum npoo, thiab lwm yam.
Rusting
Rusting yog cov txheej txheem tshuaj, uas feem ntau nrog cov hlau uas muaj hlau. Hauv lwm lo lus, cov txheej txheem corrosion tshwm sim thaum muaj hlau, nws yog hu ua xeb. Rau rusting coj qhov chaw, yuav tsum muaj tej yam kev mob. Nyob rau hauv lub xub ntiag ntawm oxygen thiab noo noo los yog dej, hlau undergoes cov tshuaj tiv thaiv thiab tsim ib tug series ntawm hlau oxide. Cov xim liab-xim av no hu ua xeb. Yog li, xeb muaj hydrated hlau (III) oxide Fe2O3·nH2O thiab hlau. (III) oxide-hydroxide (FeO(OH), Fe(OH)3). Yog hais tias xeb pib ntawm ib qho chaw, nws yuav kis tau, thiab tag nrho cov hlau yuav tawg. Tsis tsuas yog hlau, tab sis cov hlau uas muaj hlau (alloys) kuj raug xeb.
Rrusting pib nrog kev hloov ntawm electrons ntawm hlau mus rau oxygen. Hlau atoms hloov ob lub electrons thiab tsim hlau (II) ions raws li hauv qab no.
Fe → Fe2+ + 2 e−
Oxygen tsim hydroxide ions los ntawm kev txais cov electrons nyob rau hauv lub xub ntiag ntawm dej.
O2 + 4 e– + 2 H2O → 4 OH –
Cov tshuaj tiv thaiv saum toj no tau nrawm dua thaum muaj cov kua qaub. Tsis tas li ntawd, thaum muaj electrolytes zoo li ntsev, cov tshuaj tiv thaiv yog ntxiv txhim kho. Rust muaj hlau (III) ions, yog li tsim Fe2+ undergoes redox cov tshuaj tiv thaiv, muab Fe3+raws li nram no.
4 Fe2+ + O2 4 Fe3+ + 2 O 2-
Fe3+ and Fe2+ undergo following acid base reactions with water.
Fe2+ + 2 H2O ⇌ Fe(OH)2 + 2 H+
Fe3+ + 3 H2O ⇌ Fe(OH)3 + 3 H+
Thaum kawg, cov hydrated hlau oxides yog tsim los ua xeb.
Fe(OH)2 ⇌ FeO + H2O
Fe(OH)3 ⇌ FeO(OH) + H2O
2 FeO(OH) ⇌ Fe2O3 + H2O
Qhov txawv ntawm Corrosion thiab Rusting yog dab tsi?
• Rusting yog hom corrosion.
• Thaum cov hlau los yog cov khoom uas muaj hlau ua rau corrosion, nws yog hu ua xeb.
• Rusting tsim cov hlau oxide, qhov corrosion tuaj yeem ua rau cov ntsev lossis oxides ntawm cov hlau.
