Nitric Acid Corrosion
Nitric acid yog oxidizing acid, thiab nws lub zog oxidizing intensifies nrog nce concentration thiab kub. Passivating hlau xws li txhuas, titanium, stainless hlau, thiab siab - silicon cam khwb cia hlau feem ntau yog siv los ua corrosion- cov ntaub ntawv resistant. Nitric acid muaj zog intergranular corrosion kuj, ua rau intergranular corrosion nyob rau hauv stainless hlau uas yog susceptible rau intergranular corrosion.
Rau stainless hlau siv nyob rau hauv nitric acid, tshwj xeeb tshaj yog nyob rau hauv sensitized lub xeev (xws li, ncej-weld, ncej-forged, ncej- nrum), tam sim no qauv yog mus rau ultra- carbon stainless hlau tsawg. Thaum cov ntsiab lus carbon ntawm stainless hlau raug txo kom qis dua 0.02%, tus nqi corrosion ntawm sensitized stainless hlau hauv boiling 65% nitric acid txo qis.
Stainless hlau siv nyob rau hauv nitric acid yuav tsum tau kuaj rau intergranular corrosion susceptibility. Rau cov hlau tsis muaj steel siv hauv cov concentrated nitric acid thiab dilute nitric acid siab tshaj 60℃(5% -50%), cov txheej txheem boiling nitric acid yuav tsum tau siv rau kev sim. Rau cov hlau tsis muaj hlau siv hauv dilute nitric acid (30% -50%), sulfuric acid - tooj liab sulfate- tooj liab shavings txoj kev yuav tsum tau siv rau kev kuaj. Kev ntsuas tsis tsim nyog rau cov hlau tsis muaj hlau siv hauv dilute nitric acid ntawm chav tsev kub.
When nitric acid contains oxygen ions (>0.1 g / L), nws yuav ua kom lub zog ntawm cov hlau tsis xeb thiab ua rau pitting corrosion. Hauv qhov no, molybdenum- muaj cov hlau tsis muaj steel, xws li 00Cr17Ni14Mo2 thiab 2RE69 steel (00Cr25Ni22Mo2N), raug pom zoo. Incoloy 801 (20Cr-32Ni-Ti) yog resistant rau ob qho tib si nitric acid corrosion thiab kev nyuaj siab corrosion nyob rau hauv siab -kub dej uas muaj oxygen.
Corrosion-Cov khoom siv tiv taus
I. Carbon Steel thiab Cam khwb cia hlau
Cov oxide txheej tsim los ntawm carbon steel thiab cov hlau cam khwb cia zoo tib yam hauv nitric acid yog qhov ntxeem tau thiab tsis xeb-resistant.
II. Tsis yog -Ferrous Metals
Tooj, nyiaj, txhuas, thiab npib tsib xee tsis zoo corrosion kuj nyob rau hauv nitric acid. Ntshiab aluminium thiab xeb-resistant aluminium muaj qhov zoo heev corrosion kuj nyob rau hauv fuming nitric acid nrog ib tug concentration ntawm 95% los yog siab dua, tab sis tsis resistant rau nitric acid nrog ib tug concentration hauv qab no 85%, txawm nyob rau hauv chav tsev kub. Thaum cov nitric acid concentration ntau tshaj 95%, txhuas qhov corrosion kuj zoo dua li ntawm 18-8 stainless hlau.
Titanium muaj kev tiv thaiv zoo heev hauv nitric acid ntawm txhua qhov kub thiab txias hauv qab nws qhov kub kub. Tus nqi corrosion ntawm titanium nyob rau hauv siab -kub nitric acid nce nrog nce kub. Tus nqi corrosion ntawm titanium yog siab tshaj ntawm nruab nrab concentrations ntawm nitric acid, txo qis thaum lub concentration nce. Tus nqi corrosion nce mus txog qhov siab tshaj plaws ntawm 240 degree, txo qis dua 240 degree. Nyob rau hauv fuming nitric acid, thaum NO2 ntau tshaj 2% thiab cov ntsiab lus dej tsis txaus, titanium thiab nitric acid tuaj yeem hnov qab exothermically, ua rau tawg. Kev tawg tuaj yeem zam tau thaum cov dej hauv nitric acid ntau dua 2%. Qhov tshwm sim ntawm titanium ua rau tawg hauv fuming nitric acid nyob ntawm NO2 thiab dej cov ntsiab lus hauv nitric acid.
(III) Stainless hlauCustomized Stainless Hlau Phaj
Stainless hlau tseem yog cov khoom siv feem ntau hauv cov khoom siv nitric acid. Cr13 stainless hlau pom zoo corrosion kuj nyob rau hauv dilute nitric acid nyob rau hauv chav tsev kub. Cr17 stainless hlau qhia tau hais tias zoo corrosion kuj nyob rau hauv dilute acids ntawm ntau yam kub hauv qab lawv boiling point nyob rau hauv ib txwm siab. Thaum Cr13 thiab Cr17 stainless hlau yog haum rau siv nyob rau hauv nitric acid nyob rau hauv cov nqe lus ntawm corrosion kuj, lawv tau raug hloov los ntawm 18-8 austenitic steel vim lawv tsis zoo ua hauj lwm. Austenitic steel pom zoo corrosion kuj nyob rau hauv nitric acid dua ferritic steel . 18-8 steel tsuas yog siv tau nyob rau hauv chav tsev kub nyob rau hauv concentrated nitric acid thiab tsis haum rau high kub. Molybdenum{12}}muaj cov hlau tsis muaj hlau feem ntau tsis siv hauv nitric acid; Nws tsuas yog thaum nitric acid muaj chloride ions uas molybdenum-muaj stainless hlau tuaj yeem txhim kho pitting corrosion kuj.
(IV) Nickel{0}}Based Alloys
Ntau cov nickel-raws li alloys nrog cov ntsiab lus siab chromium pom zoo corrosion kuj nyob rau hauv nitric acid, xws li Hastelloy C.
