Galvanic corrosion tshwm sim thaumstainless hlau(cathode) thiab carbon steel (anode) yog hluav taws xob txuas nrog hauv electrolyte - cov pa roj carbon steel corrodes sacrificially thaum stainless hlau tseem tiv thaiv.
Lub electrochemical muaj peev xwm sib txawv ntawm passive 304 stainless hlau thiab carbon hlau yog kwv yees li 0.7 txog 1.0 V (SHE), loj txaus los tsav aggressive corrosion.
Qhov teeb meem tsim kev phom sij tshaj plaws yog thaj chaw me me ntawm cov pa roj carbon steel ua ke rau thaj tsam loj stainless hlau, uas ua rau txhua qhov corrosion mus rau qhov me me anodic nto - ua kom tsis ua hauj lwm los ntawm 10 mus rau 100 zaug.
Kev tiv thaiv ua raws li peb txheej: cov khoom siv sib xws, kev sib cais hluav taws xob, thiab kev tswj ib puag ncig.
Kev lag luam cov qauv ASTM G71, ASTM G82, thiab AMPP (yav tas los NACE) muab cov kev sim thiab kev qhia tshwj xeeb rau kev tswj xyuas galvanic corrosion.
Key Stats ntawm ib Glance
|
Metric |
Tus nqi |
|
Muaj peev xwm sib txawv (304 SS passive vs. carbon steel) |
0.7-1.0V (SHE) |
|
Corrosion tus nqi acceleration (me me anode / loj cathode) |
10 to 100 x |
|
Tus nqi galvanic corrosion nyob rau hauv seawater (carbon steel anode) |
0.5-1.5 hli / xyoo |
|
Kev sib koom ntawm kev lag luam piping tsis ua hauj lwm los ntawm galvanic corrosion |
15 mus rau 20% |
|
Tus nqi nruab nrab ntawm kev kho tsis tau galvanic corrosion |
$50,000 txog $500,000 ib qhov xwm txheej |
|
ASTM tus qauv rau kev kuaj galvanic corrosion |
ASTM G71 |
|
ASTM tus qauv rau kev txiav txim siab galvanic series |
ASTM G82, ASTM G82 |
|
Txoj kev tiv thaiv thawj zaug |
Kev xaiv cov khoom siv, kev sib cais hluav taws xob, txheej txheej, tiv thaiv cathodic |
Taw qhia
Hauv kev lag luam piping systems, offshore platforms, thiab tshuaj nroj tsuag thoob ntiaj teb, tus neeg tua neeg uas ntsiag to thov ntau lab nyiaj daus las hauv kev kho tsis tau npaj txhua xyoo:galvanic corrosion ntawm stainless hlau thiab carbon hlau. Thaum ob cov hlau no kov nyob rau hauv lub xub ntiag ntawm noo noo, ib tug invisible roj teeb daim ntawv. Cov pa roj carbon steel dhau los ua qhov kev txi rau anode, dissolving tam sim ntawd thaum stainless hlau nyob twj ywm pristine. Qhov tshwm sim? Tawg flanges, ua tsis tiav fasteners, thiab kev puas tsuaj ntawm cov txheej txheem tsis ua haujlwm - tag nrho los ntawm kev saib xyuas tus qauv uas tuaj yeem tiv thaiv tau.
Phau ntawv qhia no piav qhia txog kev tshawb fawb tom qab galvanic corrosion, maps cov xwm txheej ib puag ncig uas ua rau nws nrawm dua, thiab muab cov tswv yim tsim qauv tsim nyog hauv ASTM thiab AMPP (NACE) cov qauv. Txawm hais tias koj tab tom qhia cov ntaub ntawv rau lub raj xa dej tshiab lossis teeb meem kev teeb tsa uas twb muaj lawm, tsab xov xwm no muab kev paub txog engineering rau koj los tsim galvanic corrosion tawm ntawm koj qhov project.
Galvanic Corrosion yog dab tsi?
Galvanic corrosion yog cov txheej txheem electrochemical uas ib qho hlau corrodes nyiam dua thaum nws nyob hauv hluav taws xob tiv tauj nrog cov hlau zoo dua nyob rau hauv lub xub ntiag ntawm electrolyte.Xav tias nws yog lub roj teeb: ob lub hlau sib txawv ua raws li cov khoom siv hluav taws xob, cov dej noo ua raws li cov roj teeb, thiab cov hlau tsis zoo (cov anode) tau noj.
Peb Cov Cai
Galvanic corrosion yuav tsum muaj peb yam xwm txheej kom muaj nyob ib txhij. Tshem tawm ib qho, thiab qhov corrosion nres:
Ob qhov sib txawv ntawm cov hlau uas muaj peev xwm sib txawv electrochemical (piv txwv li, stainless hlau thiab carbon hlau).
Kev sib cuag hluav taws xob ncaj qha nruab nrab ntawm ob lub hlau (hlau- mus rau -hlau kov lossis los ntawm txoj kev conductive).
Ib qho electrolyte txuas ob qho tib si hlau - dej, noo noo, ntsev tsuag, acid condensate, los yog av noo.
Vim li cas nws tseem ceeb:Tsis zoo li niaj hnub corrosion, uas thins hlau maj mam thiab kwv yees, galvanic corrosion yog localized thiab txhoj puab heev. Nws tuaj yeem perforate carbon steel tivthaiv hauv lub hlis ntau dua li xyoo. Hauv kev nyab xeeb- cov ntawv thov tseem ceeb - cov hlab ntsha siab, cov kav dej hauv qab hiav txwv, kev sib txuas ntawm cov qauv - qhov kev nrawm nrawm no tuaj yeem ua rau tsis pom kev tsis pom kev, vim tias cov hlau tsis huv zoo li zoo tag nrho.
Vim li cas Stainless Hlau thiab Carbon Steel tsim ib qho kev phom sij Galvanic khub?
Stainless hlau yog qhov tseem ceeb tshaj plaws (cathodic) ntau dua li cov pa roj carbon steel hauv galvanic series, tsim kom muaj qhov sib txawv ntawm 0.7 txog 1.0 V uas ua rau muaj kev kub ntxhov ntawm cov hlau.Qhov loj dua qhov muaj peev xwm sib txawv, lub zog tsav lub zog rau galvanic corrosion.
Galvanic Series piav qhia
Cov galvanic series qeb hlau los ntawm lawv cov peev txheej electrochemical hauv ib puag ncig. Qhov sib nrug ntxiv ntawm ob lub hlau zaum ntawm qhov ntsuas no, qhov ntau dua lub zog tsav tsheb. Ntawm no yog qhov chaw txheeb ze ntawm cov hlau sib xws:
|
Hlau / Alloy |
Kwv yees muaj peev xwm (V vs. SHE) |
Lub luag hauj lwm nyob rau hauv khub niam txiv |
|
Magnesium |
-1.60 - 1.30 Nws |
Muaj zog anode |
|
Zinc |
-0.80 - 0.70 Nws |
Anode |
|
Cov pa roj carbon steel |
-0.60 - 0.70 Nws |
Anode (kev txi) |
|
Aluminium alloys |
-0.50 - 0.80 Nws |
Anode |
|
304 SS (ua haujlwm) |
-0.50 - 0.30 Nws |
Me me anode |
|
Coj |
-0.30 - 0.20 Nws |
Me me anode |
|
Tooj |
-0.10 - 0.00 Nws |
Cathode |
|
304 SS (tsis suav) |
+0.10 rau +0.30 |
Muaj zog cathode |
|
Nickel alloys (piv txwv li, C-276) |
+0.20 rau +0.40 |
Muaj zog cathode |
|
Graphite |
+0.30 rau +0.50 |
Muaj zog cathode |
Kev nkag siab tseem ceeb:Cov pa roj carbon steel zaum ze ntawm anodic kawg ntawm kwv yees li -0.60 txog -0.70 V, thaum passive 304 stainless hlau zaum ntawm +0.10 rau +0.30 V. Qhov sib txawv ntawm 0.7 mus rau 1.0 V yog loj heev - piv rau ib lub roj teeb ib leeg. Cov hlau tsis muaj steel ua raws li cathode (tiv thaiv), thiab carbon steel ua raws li anode (corroding).
Passive zaj duab xis tseem ceeb:Stainless hlau qhov corrosion kuj los ntawm nyias chromium - oxide passive txheej. Thaum cov txheej txheem no tsis zoo (passive xeev), stainless hlau yog qhov zoo heev. Yog tias cov txheej txheem dhau mus (lub xeev nquag) -- vim yog cov tshuaj chloride nres, crevice corrosion, lossis kev puas tsuaj rau cov khoom siv hlau - stainless hlau lub peev xwm poob los ze zog rau cov hlau, txo cov galvanic tsav tsheb. Txawm li cas los xij, kev cia siab rau cov txheej txheem txheej txheej dhau los raws li kev tiv thaiv kev tiv thaiv corrosion tsis muaj kev ntseeg siab lossis pom zoo.
Dab tsi Environmental Factors Accelerate Galvanic Corrosion?
Chloride concentration, kub, av noo, thiab electrolyte conductivity yog plaub yam accelerators ib puag ncig accelerators -- chloride-cov kabmob ib puag ncig zoo li dej hiav txwv thiab ntug hiav txwv cua yog nyob deb ntawm qhov hnyav tshaj plaws.Kev nkag siab txog cov xwm txheej no yog qhov tseem ceeb rau kev ntsuas kev pheej hmoo thiab cov khoom siv tshwj xeeb.
|
Ib puag ncig |
Corrosivity |
Tus nqi Galvanic (mm / xyoo) |
Qhov Tseem Ceeb Risk Factor |
|
Hauv tsev, qhuav, huab cua- tswj tau |
Tsawg heev |
< 0.01 |
Tsis muaj electrolyte ruaj khov |
|
Nyob deb nroog |
Tsawg |
0.01-0.05 Nws |
Nroj tsuag los nag |
|
Nroog / industrial cua |
Nruab nrab |
0.05-0.15 Nws |
SO2 thiab cov pa phem deposition |
|
Ntug hiav txwv cua (ntsev ntsev tsuag) |
Siab |
0.15-0.50 Nws |
Chloride deposition |
|
Dej hiav txwv immersion |
Siab heev |
0.50-1.50 Nws |
High Cl - + siab conductivity |
|
Brine / tshuaj txheej txheem dej |
Heev |
1.00 rau 5.00+ |
High Cl - + pH qis + elevated temp |
|
Av (siab noo noo, tsis tshua muaj resistivity) |
Siab |
0.10-0.50 Nws |
Kev sib txawv tsis sib xws + microbes |
Plaub Accelerators nyob rau hauv nthuav dav
1. Chloride Concentration:Chloride ions (Cl-) yog tib hom kev puas tsuaj rau galvanic corrosion. Lawv nce electrolyte conductivity (kev thauj mus los ntawm electron ceev) thiab hauv zos nkag mus rau stainless hlau cov yeeb yaj kiab passive, tsim cov chaw pitting uas txuas ntxiv ua rau ob peb galvanic. Cov dej hiav txwv (kwv yees li 19,000 ppm Cl-) yog ib qho ntawm cov khoom siv hluav taws xob zoo tshaj plaws.
2. Kub:Txhua txhua 10 degrees C nce nyob rau hauv qhov kub thiab txias tuaj yeem ua ob npaug ntawm tus nqi corrosion los ntawm kev nrawm electrochemical kinetics. Cov txheej txheem dej kub, qhov chaw ib puag ncig, thiab huab cua sov ua kom muaj zog galvanic corrosion heev. Qee zaum, qhov kub siab kuj tseem hloov cov galvanic series, hloov qhov sib txawv ntawm cov hlau.
3. Humidity and Wetness Duration:Galvanic corrosion yuav tsum tau ua cov yeeb yaj kiab tsis tu ncua electrolyte. Nyob rau hauv ib puag ncig nrog cov av noo siab (ntau tshaj 60%), cov yeeb yaj kiab nyias nyias nyob ntawm cov hlau, txhawb nqa cov khoom siv hluav taws xob. Cov ntug dej hiav txwv nrog ntsev pos huab deposition yog qhov txaus ntshai tshwj xeeb vim tias cov ntsev zaj duab xis absorbs noo noo (deliquescence), tswj cov electrolyte kev pab cuam txawm nyob rau nruab nrab cov av noo.
4. Electrolyte Conductivity:Qhov ntau conductive cov electrolyte, qhov dav ntawm cov galvanic ob peb cheeb tsam. Cov dej ntshiab muaj cov khoom siv hluav taws xob tsawg thiab txwv galvanic corrosion rau thaj tsam tam sim ntawd. Seawater thiab brine muaj cov conductivity siab, txuas cov galvanic influence centimeters los yog txawm meters los ntawm cov hlau tiag tiag - mus rau - hlau hlws ris.
Yuav Ua Li Cas Anode-rau-Cathode Area Ratio Control Corrosion Severity?
Ib qho me me anode (carbon steel) ua ke rau lub cathode loj (stainless steel) concentrates tag nrho cov galvanic tam sim no mus rau qhov chaw me me, ua kom corrosion los ntawm 10 mus rau 100 zaug -- qhov txaus ntshai tshaj plaws thiab feem ntau tsim teeb meem hauv cov tshuab hlau sib txawv.Qhov no yog hu ua qhov tsis zoo cheeb tsam piv, thiab nws yog ib qho tseem ceeb tshaj plaws geometric yam nyob rau hauv galvanic corrosion tsim.
Yog vim li cas lub Cheeb Tsam Ratio Dominates
Galvanic tam sim no yog tsav los ntawm cov tshuaj tiv thaiv cathodic (cov pa txo qis lossis hydrogen evolution) ntawm cov hlau tsis huv. Ib cheeb tsam cathode loj txhais tau tias tag nrho cov cathodic tam sim no loj. Tag nrho cov tam sim no yuav tsum ntws los ntawm anode (carbon steel). Yog hais tias lub anode me me, qhov ceev tam sim no ntawm qhov anode nto dhau los ua qhov hnyav - lub ntsiab lus ntawm corrosion ntawm ib chav tsev skyrockets.
|
Anode: Cathode Area Ratio |
Tus nqi Multiplier |
Risk Level |
Hom Scenario |
|
1: 1 (qhov sib npaug) |
1 x (lub hauv paus) |
Tsawg |
Pav ca phaj sib koom tes, sib npaug thickness |
|
1 : 5 |
3a5x ua |
Nruab nrab |
Carbon steel fastener nyob rau hauv SS phaj |
|
1 : 10 |
5 a10x |
Siab |
CS ntxhua khaub ncaws hauv qab SS ntsia liaj qhov rooj taub hau |
|
1 : 50 |
20 a 50 x |
Mob hnyav |
CS fastener txuas loj SS panels |
|
1 : 100+ |
50-100 x |
Tseem ceeb |
Me CS rivet / weld nyob rau hauv loj SS qauv |
Golden Txoj Cai ntawm Cheeb Tsam Ratio
Ib txwm nyiam thaj chaw anode loj thiab thaj chaw me me cathode.Yog tias koj yuav tsum siv cov hlau tsis sib xws, ua kom cov hlau tsis zoo (carbon steel) cov khoom loj dua thiab cov hlau tsis zoo (stainless steel) cov khoom me me. Piv txwv li, siv stainless hlau fasteners los koom nrog cov pa roj carbon steel daim hlau feem ntau tau txais - qhov loj carbon steel cheeb tsam ua raws li ib tug loj anode, kis corrosion thinly. Qhov rov qab - carbon steel fasteners nyob rau hauv stainless hlau daim hlau - yog ib daim ntawv qhia rau fastener tsis ua hauj lwm.
Tswv yim piv txwv:Nyob rau hauv lub flanged yeeb nkab kev twb kev txuas uas ib tug stainless hlau yeeb nkab mates nrog ib tug carbon steel flange, cov pa roj carbon steel flange yuav tsum yog cov loj, thicker tivthaiv. Zoo dua, qhia meej cov pa roj carbon steel flange nrog weld overlay ntawm cov khoom siv sib xws, lossis siv cov khoom siv flange cais kom tawg tag nrho.
Yuav ua li cas xaiv cov khoom tshem tawm Galvanic Corrosion Risk ntawm qhov chaw?
Xaiv cov hlau uas nyob ib sab ntawm cov galvanic series (qhov muaj peev xwm sib txawv hauv qab 0.25 V) yog txoj hauv kev txhim khu kev qha tshaj plaws los tshem tawm cov galvanic corrosion ntawm cov qauv tsim - tsis muaj kev sib cais, txheej txheej, lossis kev saib xyuas yuav tsum tau ua.Kev xaiv cov khoom siv yog thawj thiab muaj zog tshaj plaws ntawm kev tiv thaiv.
Material Compatibility Strategy
Thaum cov hlau tsis muaj hlau yuav tsum tau siv, xav txog cov kev hloov pauv no rau cov hlau tsis sib xws rau cov khoom sib txuas:
|
Coupled nrog stainless hlau |
Kev sib haum xeeb |
Muaj peev xwm Diff (V) |
Kev pom zoo |
|
304 / 316 / 317 SS (ib tsev neeg) |
Zoo heev |
< 0.05 |
Kev xyaum zoo tshaj plaws - tsis muaj kev pheej hmoo galvanic |
|
Duplex SS (2205, 2507) |
Zoo heev |
< 0.10 |
Tau tshaj; txheeb xyuas qhov chaw pabcuam |
|
Nickel alloys (825, 625, C-276) |
Zoo |
0.05-0.20 Nws |
me ntsis noble; muaj kev nyab xeeb nyob rau hauv feem ntau |
|
Tooj thiab tooj dag |
Nruab nrab |
0.30-0.50 Nws |
Cais tawm hauv ib puag ncig nruj |
|
Cov pa roj carbon steel |
pluag |
0.70 - 1.00 Nws |
cais lossis zam; siv cov kev hloov kho alloy |
|
Aluminium alloys |
pluag |
0.50 - 1.00 Nws |
cais tawm; Al ua sacrificial anode |
|
Zinc (galvanized hlau) |
Neeg pluag heev |
0.80-1.20 Nws |
Zinc corrodes sai heev; yeej tsis ncaj- khub niam txiv |
Txhim kho Carbon Steel Cheebtsam
Thaum cov peev nyiaj tso cai, qhov kev daws teeb meem huv tshaj plaws yog txhawm rau txhim kho cov khoom siv carbon steel rau stainless hlau lossis npib tsib xee alloys hauv tib tsev neeg qib.Rau flanges thiab fasteners tshwj xeeb, xav txog:
Hloov cov pa roj carbon steel flanges nrog 304/316L stainless hlau flanges ntawm tib lub siab ntsuas.
Siv 316 stainless hlau fasteners (bolts, txiv ntseej, ntxhua khaub ncaws) es tsis txhob carbon steel fasteners thaum koom nrog stainless hlau Cheebtsam.
Rau siab -chloride los yog acidic kev pab cuam, qhia meej duplex stainless hlau (2205 los yog 2507) los yog npib tsib xee alloys (Alloy 625, Alloy 825) rau ob qho tib si structural thiab kev koom ua ke Cheebtsam.
Thaum cov pa roj carbon steel yuav tsum tau khaws cia rau tus nqi yog vim li cas, siv weld overlay los yog cladding nrog stainless hlau los yog npib tsib xee alloy ntawm wetted nto.
Tus nqi- ntawv ceeb toom:Thaum kev kho dua tshiab rau cov hlau tsis muaj hlau lossis npib tsib xee alloys nce cov khoom siv ua ntej los ntawm 2 mus rau 5 zaug, nws tshem tawm cov nqi ntawm kev sib cais ntawm kev tu, txheej txheej, thiab tsis ua hauj lwm - feem ntau txuag 3 mus rau 10 npaug ntawm tus nqi pib tshaj 20 xyoo kev pab cuam lub neej.
Cov tswv yim tsim dab tsi rhuav tshem Galvanic Circuit Court?
Kev rhuav tshem cov hluav taws xob hluav taws xob ntawm cov hlau tsis sib xws uas siv cov teeb meem kev sib cais, kev sib cais geometry, lossis cov qauv tsim tawm tshem tawm cov galvanic cell ntawm lub cev - cov kab thib ob ntawm kev tiv thaiv thaum cov khoom siv sib xws tsis ua tau.Kev tsim qauv zoo ua rau galvanic corrosion lub cev tsis tuaj yeem, tsis yog qhov ntsuas tsis zoo.
Tswv yim 1: Kev cais hluav taws xob
Nruab cov ntaub ntawv insulating ntawm txhua lub hlau - mus rau - hlau hlws ris kom tawg hluav taws xob Circuit Court:
|
Isolation Component |
Yam khoom |
Qhov twg siv |
Temp txwv |
|
Insulating gasket |
PTFE / EPDM / Neoprene |
Nruab nrab ntawm lub ntsej muag flange |
200-250 C |
|
Insulating lub tes tsho / bushing |
G-10 fiberglass / PTFE |
Nyob ib ncig ntawm bolt shanks |
180-260 C |
|
Insulating washers |
G-10 / Nylon / PTFE |
Hauv qab bolt taub hau thiab ceev |
180-260 C |
|
Dielectric flange khoom siv |
Gasket + tes tsho + washers |
Ua kom tiav flange cais |
Rau cov khoom siv gasket |
Daim ntawv tseem ceeb ntawm installation:Cov khoom siv cais tawm tsuas yog siv tau yog tias TXHUA peb yam khoom (gasket, lub tes tsho, thiab ntxhua khaub ncaws) raug teeb tsa kom raug. Ib lub tshuab ntxhua khaub ncaws uas ploj lawm hauv qab lub taub hau ntsia hlau tsim cov hlau - rau - hlau luv uas ua rau tag nrho cov khoom siv tsis raug. Ib txwm txheeb xyuas kev sib cais nrog kev ntsuas kev tiv thaiv tom qab sib dhos - lub hom phiaj tiv thaiv yuav tsum tshaj 1,000 ohms.
Tswvyim 2: Tsis txhob tso dej twj thiab crevices
- Tsim geometry los tiv thaiv electrolyte tsub zuj zuj ntawm qhov sib txawv -hlau junctions:
- Tsim cov dej nqes hav deb ntawm flanged pob qij txha thiab sib xyaw- hlau txuas.
- Tsis txhob muaj kab rov tav tiaj qhov chaw uas cov dej tuaj yeem ua pas dej ze ze ntawm cov hlau sib txawv.
- Siv tag nrho -kev nkag welds es tsis txhob ntawm lub puab tsaig pob qij txha los yog riveted kev twb kev txuas qhov twg ua tau -- welds tshem tawm qhov sib txawv crevice uas ntxiab electrolyte.
- Yog tias cov pob qij txha tsis tuaj yeem zam tau, muab qhov sib txawv nrog cov khoom sib txuas kom tsis txhob muaj cov electrolyte nkag mus.
Lub tswv yim 3: Tswj Kev Siv Tau Zoo rau Kev Tshuaj Xyuas
Tsim rau inspectability:Txawm tias muaj kev tiv thaiv zoo tshaj plaws, galvanic corrosion tseem tuaj yeem tshwm sim vim yog txheej txheej puas, gasket degradation, lossis tsis pom qhov hloov pauv ib puag ncig. Xyuas kom meej tias qhov sib txawv ntawm - hlau sib txuas yog siv tau rau kev soj ntsuam lub sij hawm tsis pom kev thiab tsis yog - kuaj kev puas tsuaj (kev ntsuas ultrasonic thickness, eddy tam sim no, lossis radiography).
Yuav Ua Li Cas Insulation Barriers thiab Coatings Ua Haujlwm hauv Kev Xyaum?
Cov txheej txheej thiab cov txheej thaiv thaiv tiv thaiv electrolyte tiv tauj nrog cov hlau nto, thaum kev tiv thaiv cathodic hloov lub peev xwm ntawm tag nrho cov kab ke - ob qho tib si yog cov kev tiv thaiv theem nrab thaum kev sib cais ib leeg tsis txaus.Lub hauv paus ntsiab lus tseem ceeb: tsis txhob coated tsuas yog lub anode (carbon steel) thaum tawm hauv cathode (stainless steel) liab qab.
Txheej Txheej Txheej Txheem: Txoj Kev Tsis Ncaj Ncees vs
Qhov feem ntau txheej txheej yuam kev:Siv cov txheej txheem tiv thaiv tsuas yog rau cov pa roj carbon steel (anode) thaum tawm hauv cov hlau tsis muaj steel (cathode) liab qab. Qhov no yog kev puas tsuaj. Yog tias lub hnub so txheej txheej (pinhole, khawb, lossis nti) nthuav tawm txawm tias thaj tsam me me ntawm cov pa roj carbon steel, tag nrho cov galvanic tam sim no los ntawm qhov loj liab qab stainless hlau cathode concentrates rau qhov me me raug anode - tsim kom muaj qhov tsis zoo ntawm cheeb tsam thiab perforation ceev.
Txoj kev kom raug:Coated ob leeg hlau, los yog lub tsho tsuas yog lub cathode (stainless hlau). Yog tias cov hlau tsis muaj hlau yog coated, qhov chaw zoo cathode shrinks, txo tag nrho cov galvanic tam sim no txawm tias qhov chaw me me ntawm cov hlau raug nthuav tawm. Qhov no yog lub hauv paus ntsiab lus txheej txheem rau galvanic corrosion tswj: txo cov cathode cheeb tsam, tsis txhob muaj qhov anode cheeb tsam ib leeg.
|
Txheej Txheej Txheem |
Anode (CS) |
Cathode (SS) |
Kev pheej hmoo yog tias txheej tsis tiav |
Kev pom zoo |
|
Tsis muaj txheej |
Tsis muaj |
Tsis muaj |
Baseline galvanic corrosion kuj |
Tsuas yog nyob rau hauv qhuav sab hauv tsev env. |
|
Anode nkaus xwb (feem ntau yuam kev) |
Yog lawm |
Tsis muaj |
EXTREME - concentrated tsis ua hauj lwm |
Tsis pom zoo |
|
Cathode nkaus xwb |
Tsis muaj |
Yog lawm |
Tsawg - txo qhov chaw cathode |
Zoo rau qhov chaw me me |
|
Ob leeg hlau |
Yog lawm |
Yog lawm |
Tsawg - ob qho tib si tiv thaiv |
Kev coj ua zoo tshaj plaws rau kev pabcuam nruj |
|
Galvanize CS + txheej SS |
Yog (Zn) |
Yog lawm |
Tsawg heev -- Zn kev txi |
Txaus siab rau atmospheric |
Hom Kev Tiv Thaiv Txheej Txheem
Xaiv cov txheej txheem raws li qhov chaw ua haujlwm, qhov kub thiab txias, thiab raug tshuaj lom neeg:
Epoxy txheej: Cov tshuaj tiv thaiv zoo heev, tsim nyog rau kev pabcuam immersion txog 120 degrees C. Ob -ib feem epoxy systems yog tus qauv rau kev siv sab nrauv thiab cov nroj tsuag tshuaj.
Polyurethane topcoats: UV-resistant, ruaj rau atmospheric raug. Feem ntau siv epoxy primer rau ib qho kev ua tiav.
Kub-dip galvanizing: Deposits ib txheej zinc txheej ntawm carbon steel. Cov zinc corrodes nyiam dua, tiv thaiv ob qho tib si carbon steel substrate thiab txo qhov sib txawv ntawm cov hlau tsis muaj steel. Txawm li cas los xij, zinc yog anodic heev rau stainless hlau - kev sib cuag ncaj qha ntawm galvanized steel thiab stainless hlau tseem yuav tsum tau zam los yog cais.
PTFE / fluoropolymer txheej: Tshuaj inertness thiab tsis tshua muaj kev sib txhuam. Haum rau qhov chaw gasket thiab fastener coatings qhov twg tshuaj tiv thaiv yog qhov tseem ceeb.
Kev tiv thaiv Cathodic ua ib qho ntxiv
Sacrificial anode lossis impressed tam sim no cathodic tiv thaiv (ICCP) tuaj yeem hloov tag nrho lub cev tsis zoo, tiv thaiv cov pa roj carbon steel.Hauv subsea thiab faus cov raj xa dej, kev tiv thaiv cathodic yog qhov yuav tsum tau ua raws li AMPP (NACE) SP0169. Txawm li cas los xij, kev tiv thaiv cathodic tsis hloov qhov xav tau rau txheej txheej thiab kev cais tawm -- nws ntxiv rau lawv. Kev tiv thaiv ntau dhau tuaj yeem ua rau txheej txheej disbondment thiab hydrogen embrittlement ntawm high-strength steels.
Dab tsi yog Kev Lag Luam Cov Qauv Tswj Kev Tiv Thaiv Galvanic Corrosion?
ASTM G71, ASTM G82, ASTM G104, thiab AMPP (NACE) SP0169 yog cov txheej txheem tseem ceeb tswj kev kuaj galvanic corrosion, galvanic series kev txiav txim siab, thiab kev tswj kev xeb hauv kev lag luam.Kev ua raws li cov qauv no qhia tau hais tias muaj kev mob siab rau engineering thiab feem ntau yuav tsum tau ua los ntawm cov cai (ASME B31.3, API 510, API 570) rau cov txheej txheem kav dej thiab cov hlab ntsha siab.
|
Txuj |
Title / Scope |
Dab tsi Nws npog |
Thaum twg los thov |
|
ASTM G71 |
Galvanic Corrosion Tests hauv Electrolytes |
Lab thiab teb xeem txoj kev rau galvanic khub niam txiv |
Validating cov khoom khub rau kev tsim tshiab |
|
ASTM G82, ASTM G82 |
Galvanic Series rau Predicting Performance |
Yuav ua li cas tsim thiab siv galvanic series |
Xaiv cov khoom siv rau cov khoom siv electrolyte |
|
ASTM G 104 1 |
Galvanic Corrosion nyob rau hauv Atmospheric tej yam kev mob |
Sab nraum zoov raug kuaj ntawm galvanic khub niam txiv |
Sab nraum cov qauv thiab atmospheric kev pab cuam |
|
ASTM A 380 Cov Lus Qhia Tshwj Xeeb |
Passivation ntawm Stainless hlau qhov chaw |
Cov txheej txheem los kho chromium- oxide passive zaj duab xis |
Tom qab fabrication, vuam, los yog paug |
|
PAB SP0169 |
Sab nrauv Corrosion ntawm Underground / Submerged Piping |
Cathodic tiv thaiv yuav tsum tau rau faus kav |
Yuav tsum tau faus/subsea pipelines |
|
TIAB SA SP0176 |
Corrosion Control ntawm Tsaus Offshore Platforms |
Kev xaiv cov khoom siv thiab kev tiv thaiv corrosion rau offshore |
Offshore roj thiab roj platforms |
|
ASME B31.3 |
Txheej Txheem Piping |
Kev siv galvanic corrosion hauv cov khoom xaiv |
Chemical, petrochemical, refinery kav dej |
|
TS EN ISO 8044 |
Corrosion ntawm Hlau - Cov ntsiab lus tseem ceeb |
Standardized terminology rau corrosion hom |
International project documentation |
Tswv yim tswv yim:Thaum qhia txog galvanic corrosion tiv thaiv kev ntsuas ntawm engineering kos duab, siv cov qauv siv tau meej meej (xws li, 'Nruab dielectric flange cais cov khoom siv rau ASTM G71 galvanic compatibility kev soj ntsuam'). Qhov no ua kom cov neeg tsim khoom nkag siab txog qhov yuav tsum tau ua thiab tus neeg kuaj xyuas muaj qhov lees paub lees paub.
Koj Yuav Tshawb Xyuas thiab Saib Xyuas Galvanic Corrosion li cas hauv Kev Pabcuam?
Kev sib xyaw ua ke ntawm kev tshuaj xyuas qhov muag, ntsuas qhov ntsuas ultrasonic thickness, thiab kev tshuaj xyuas electrochemical muab kev pom zoo ntawm galvanic corrosion ua ntej tsis ua haujlwm.Kev soj ntsuam zaus yuav tsum muaj kev pheej hmoo-raws li, nrog rau kev soj ntsuam ntau zaus rau siab - qhov tshwm sim thiab siab - ib puag ncig corrosivity.
Kev tshuaj xyuas
|
Txoj kev |
Dab tsi Nws Pom |
Kev kuaj pom txwv |
Ntau zaus |
Zoo tshaj rau |
|
Kev kuaj pom |
Rust staining, pitting, txheej puas |
Nto qhov tsis xws luag> 0.5 mm |
Peb lub hlis twg rau txhua xyoo |
Siv tau cov kev sib txuas atmospheric |
|
Ultrasonic thickness (UT) |
Phab ntsa poob ntawm carbon steel ze junctions |
0.1 hli phab ntsa poob |
Txhua xyoo mus rau biennial |
Cov kav dej thiab cov hlab ntsha siab |
|
Eddy kev sim tam sim no |
Nto thiab ze -surface pitting |
0.2mm ib |
Raws li xav tau |
Stainless hlau nto defects |
|
Kev kuaj ntshav (RT) |
Sab hauv corrosion thiab phab ntsa poob |
5% phab ntsa poob |
Ob xyoos |
Welded pob qij txha, qhov chaw nkag tsis tau |
|
Electrochemical xyuas |
Galvanic tam sim no ntawm cov hlau sib txuas |
Microampere- qib |
Tsis tu ncua |
Tseem ceeb lossis siab - cov kev pheej hmoo siab |
|
Kev saib xyuas daim coupon |
Qhov tseeb corrosion tus nqi ntawm cov qauv kuaj |
Nyob ntawm lub sij hawm raug |
Peb lub hlis twg retrieval |
Tank, nkoj, pipelines |
Kev Saib Xyuas Txoj Haujlwm Zoo Tshaj Plaws
Muab cov ntsiab lus ntsuas qhov tuab ntawm ultrasonic (TMLs) nyob rau hauv 50 hli ntawm qhov sib txawv ntawm - hlau hlws ris - qhov no yog qhov twg galvanic corrosion concentrates.
Nruab daim coupon corrosion ua los ntawm tib qib carbon steel ntawm cov chaw sawv cev los ntsuas qhov tseeb corrosion raws li kev pabcuam.
Rau cov tshuab tseem ceeb, teeb tsa online galvanic tam sim no saib uas ntsuas qhov tseeb tam sim no ntws ntawm cov hlau txuas -- qhov no muab cov ntaub ntawv tus nqi galvanic corrosion ntawm lub sijhawm.
Khaws cov ntaub ntawv hauv paus thickness ntawm commissioning; Kev ntsuas tom qab ntsuas qhov tseeb corrosion tus nqi raws sij hawm.
Cov ntaub ntawv tag nrho cov kev soj ntsuam tshawb pom nyob rau hauv cov ntaub ntawv tswj kev tiv thaiv corrosion, taug qab cov kab sib txawv los kwv yees lub neej kev pabcuam ntxiv.
Tus nqi tiv thaiv vs. Tus nqi ntawm kev ua tsis tiav yog dab tsi?
Tus nqi ntawm kev tiv thaiv galvanic corrosion feem ntau yog 3 mus rau 10 npaug qis dua tus nqi ntawm qhov tsis tau npaj tseg - suav nrog kev kho, kev poob qis, kev tsim khoom ploj, thiab cov xwm txheej muaj kev nyab xeeb.Kev tiv thaiv tsis yog kev txiav txim siab engineering xwb - nws yog nyiaj txiag.
|
Qeb Nqi |
Txoj Kev Tiv Thaiv |
Failure Scenario |
Ratio (Fail: Tiv thaiv) |
|
Flange cais cov khoom siv (DN100) |
$200 txog $500 rau ib qho khoom siv |
$ 5,000 txog $ 20,000 ib qho xau + downtime |
10-40 x |
|
SS fastener hloov kho |
$ 2 txog $ 10 rau tus nqi them tus nqi fastener |
$ 500 txog $ 5,000 rau ib qho tsis ua haujlwm fastener |
50 rau 500x |
|
Cov khoom siv hloov kho (CS rau 316SS flange) |
$ 200 txog $ 800 tus nqi them rau ib flange |
$10,000 txog $50,000 rau ib qho kev ua tsis tiav |
12 x60 |
|
Txheej txheej (epoxy + PU) |
$50 rau $150 ib square meter |
Re-coat + moj tej tawg=$500+ ib sqm tom qab ua tsis tiav |
3 a10x |
|
Cathodic tiv thaiv (ICCP) |
$10,000 rau $50,000 ntsia |
$100,000+ rau corroded pipeline seem |
2 rau 10x |
|
Ua kom tiav cov ntaub ntawv compatibility tsim |
2 mus rau 5x cov khoom siv tus nqi hwm |
Kev hloov pauv tag nrho + kev foob |
5 txog 20x (20-xyoo lub neej) |
Cov nqi zais ntawm kev ua tsis tiav:Tshaj li cov nqi kho ncaj qha, kev ua tsis tiav galvanic ua rau cov nuj nqis cascading -- kev kaw thaum muaj xwm txheej ceev, kev tu ib puag ncig, kev nplua nyiaj, kev tuav pov hwm nce ntxiv, thiab kev puas tsuaj rau lub koob npe nrov. Nyob rau hauv kev nyab xeeb-tseem ceeb daim ntaub ntawv (offshore platforms, tshuaj reactors, subsea pipelines), ib tug galvanic corrosion tsis ua hauj lwm yuav raug nqi $ 1 lab mus rau $ 50 lab nyob rau hauv tag nrho cov kev puas tsuaj.
Txoj Cai 1-10-100
Hauv kev txhim kho corrosion, txoj cai 1-10-100 siv:Nws raug nqi $ 1 los tiv thaiv corrosion ntawm cov qauv tsim, $ 10 kom txo tau nws thaum tsim kho, thiab $ 100 los kho nws tom qab tsis ua haujlwm. Rau galvanic corrosion tshwj xeeb, qhov sib piv no feem ntau yog qhov hnyav dua vim tias qhov chaw hauv cheeb tsam ntawm qhov kev tawm tsam txhais tau tias qhov pom kev puas tsuaj tsuas yog ib feem ntawm qhov tseeb ntawm cov qauv degradation.
Thaum twg Koj Yuav Tsum Hloov Carbon Steel nrog Stainless Hlau lossis Nickel Alloys?
Thaum qhov chaw pabcuam cuam tshuam nrog cov tshuaj chlorides, qhov kub thiab txias, lossis kev nyab xeeb - cov ntawv thov tseem ceeb, kev kho dua tshiab los ntawm cov pa roj carbon steel rau stainless hlau lossis npib tsib xee alloys tsis xaiv tau - nws yog lub luag haujlwm kev txiav txim siab engineering.Qhov kev txiav txim siab hloov kho yuav tsum yog raws li kev soj ntsuam kev pheej hmoo raug txiav txim siab ib puag ncig hnyav, qhov tshwm sim ntawm kev ua tsis tiav, thiab kev lag luam hauv lub neej.
Txoj Kev Txiav Txim Siab
|
Kev Pabcuam |
Khoom siv pom zoo |
Kev xav |
Tseem xav tau kev cais tawm? |
|
Qhuav sab hauv tsev, <40 C, tsis muaj chlorides |
CS + SS nrog cov txheej txheem yooj yim |
Tsawg galvanic txaus ntshai; intermittent electrolyte |
Pom zoo, tsis tseem ceeb |
|
Sab nraum atmospheric, temperate |
CS + SS nrog cov khoom siv cais + txheej |
Nquag ntub / qhuav; txaus ntshai |
Yog -- tag nrho cov khoom siv dielectric |
|
Ntug hiav txwv cua (ntsev ntsev tsuag) |
Hloov kho CS mus rau 316SS lossis duplex |
Chloride deposition drives tus nqi siab |
Yog, los yog tshem tawm cov hlau tsis sib xws |
|
Dej hiav txwv immersion |
Txhim kho tag nrho cov kab ke mus rau 316SS / duplex / Ni alloy |
Muaj zog galvanic corrosion |
Tag nrho cov ntaub ntawv compatibility nyiam |
|
Cov txheej txheem tshuaj (acid / chloride) |
Nickel alloy (625, C-276, 825) thoob plaws |
Ib puag ncig huab cua; SS muaj pit |
Tsis muaj - tib tsev neeg alloy |
|
High temperature (> 200 C) |
Hloov kho mus rau 316Ti / 321 SS lossis Ni alloy |
Siab temp accelerates nres |
Siv siab -temp cais (mica) |
|
Cov kav dej faus |
CS nrog kev tiv thaiv cathodic + kev sib cais |
AMPP SP0169 txoj cai CP |
Yog - ntawm txhua qhov kev sib tshuam |
|
Khoom noj khoom haus / tshuaj |
316SS thoob plaws (tsis muaj crevices) |
Cov kev cai huv huv txwv tsis pub txheej txheej |
Tsis muaj - tib yam khoom thoob plaws |
Qhov zoo ntawm Nickel Alloy
Rau cov kev pabcuam uas xav tau tshaj plaws - cov tshuaj chloride siab, kub siab, roj qaub (H2S), lossis cov kua qaub sib xyaw - nickel alloys muab kev ua haujlwm zoo tshaj:Alloy 625 muaj kev tiv thaiv zoo heev rau chloride pitting thiab kev ntxhov siab corrosion tawg mus txog 650 degrees C. Alloy 825 muab kev ua tau zoo hauv kev pabcuam sulfuric thiab phosphoric acid. Alloy C-276 yog tus qauv kub rau cov tshuaj lom neeg nruj tshaj plaws, tiv thaiv oxidizing thiab txo cov kua qaub. Los ntawm kev qhia cov nickel alloys thoob plaws hauv lub cev, koj tshem tawm galvanic corrosion nkaus thaum tau txais kev tiv thaiv zoo tshaj hauv zos.
Cov lus nug nquag
Kuv puas tuaj yeem siv stainless hlau bolts ntawm carbon steel flanges yam xyuam xim?
Yog - qhov no feem ntau muaj kev nyab xeeb vim tias thaj tsam piv rau qhov loj anode (carbon steel flange) thiab me me cathode (stainless steel bolts).Qhov me me ntawm galvanic tam sim no los ntawm cov ntsia liaj qhov rooj qhov chaw kis thoob plaws thaj chaw loj carbon steel flange, ua kom tus nqi corrosion ntawm ib cheeb tsam tsawg. Txawm li cas los xij, nyob rau hauv dej hiav txwv los yog siab - ib puag ncig chloride, koj yuav tsum tseem siv cov txheej txheem rau cov pa roj carbon steel flange thiab siv cov tshuab ntxhua khaub ncaws cais kom ntev kev pab cuam. Cov kev teeb tsa rov qab (cov pa roj carbon steel bolts ntawm stainless hlau flanges) yog qhov txaus ntshai thiab yuav tsum zam.
Nws siv sijhawm ntev npaum li cas rau galvanic corrosion ua rau tsis ua haujlwm?
Hauv dej hiav txwv, galvanic corrosion ntawm stainless hlau thiab carbon hlau tuaj yeem perforate 5 hli carbon steel phab ntsa hauv 3 mus rau 10 xyoo; Hauv cov xwm txheej hnyav nrog qhov tsis zoo ntawm thaj chaw, qhov tsis ua haujlwm tuaj yeem tshwm sim hauv qis dua 12 lub hlis.Nyob rau hauv qhov chaw qhuav hauv tsev, galvanic corrosion tej zaum yuav negligible rau tag nrho cov tsim lub neej. Tus nqi corrosion nyob ntawm cov electrolyte (chloride concentration, conductivity, kub), thaj tsam piv, thiab seb puas muaj kev sib cais lossis txheej txheej. Ib txwm ua ib qhov chaw -kev ntsuas kev pheej hmoo tshwj xeeb.
Puas yog pleev xim rau carbon steel tiv thaiv galvanic corrosion?
Painting tsuas yog cov pa roj carbon steel (anode) yog qhov tsis ncaj ncees lawm thiab tuaj yeem ua rau corrosion tsis zoo.Yog hais tias lub txheej muaj ib tug pinhole los yog khawb, tag nrho cov galvanic tam sim no los ntawm lub loj liab qab stainless hlau cathode concentrates ntawm qhov chaw me me, ua rau perforation ceev. Lub tswv yim kom raug yog los npog ob qho tib si hlau, los yog lub tsho tsuas yog cov hlau tsis muaj hlau (cathode) kom txo tau qhov chaw zoo cathode. Qhov no yog ib qho ntawm feem ntau thiab txaus ntshai yuam kev hauv kev tiv thaiv galvanic corrosion.
Puas yog galvanic corrosion yog ib qho teeb meem nrog galvanized steel thiab stainless hlau?
Yog lawm - galvanized steel (zinc txheej) yog anodic ntau dua li cov pa roj carbon monoxide thaum ua ke nrog cov hlau tsis muaj steel, ua rau ob peb galvanic hnyav dua.Zinc zaum ntawm kwv yees li -0.80 V ntawm cov galvanic series, txog 0.1 txog 0.2 V ntau anodic ntau dua li carbon hlau. Thaum galvanized hlau tiv nrog stainless hlau, zinc txheej corrodes sai heev. Thaum cov zinc tau noj, cov pa roj carbon monoxide tseem txuas ntxiv corrode galvanically. Kev sib cuag ncaj qha ntawm galvanized steel thiab stainless hlau yuav tsum tau zam los yog hluav taws xob cais.
Dab tsi yog qhov txawv ntawm galvanic corrosion thiab crevice corrosion?
Galvanic corrosion yuav tsum muaj ob yam hlau sib txawv; crevice corrosion tuaj yeem tshwm sim ntawm ib qho hlau thiab yog tsav los ntawm oxygen concentration sib txawv hauv qhov sib txawv ntawm qhov sib txawv.Txawm li cas los xij, ob qho tib si feem ntau sib koom ua ke: flanged sib koom ua ke ntawm cov hlau tsis muaj steel thiab carbon hlau tsim ob leeg galvanic (cov hlau sib txawv) thiab qhov sib txawv (qhov sib txawv gasket). Lub crevice ntxiab electrolyte thiab tseem tuaj yeem ua rau cov hlau tsis muaj zog ntawm cov yeeb yaj kiab hauv zos, hloov cov hlau tsis muaj zog los ntawm passive (noble) mus rau active (tsawg noble), uas tuaj yeem txo cov galvanic tsav quab yuam tab sis nce hauv zos pitting. Ob lub tswv yim yuav tsum tau hais txog hauv kev tsim - siv kev sib cais los tiv thaiv galvanic corrosion thiab kev xaiv gasket kom txo qis cov crevices.
Dab tsi yog cov khoom sib cais zoo tshaj plaws rau siab -kev pabcuam kub?
Rau qhov kub siab tshaj 200 ° C, tus qauv PTFE thiab EPDM cov ntaub ntawv cais tawm degrade; siv mica-raws li gaskets lossis ceramic-fiber rwb thaiv tsev ntsuas rau qhov ntsuas kub.Rau qhov kub txog li 260 degrees C, G-10 fiberglass tes tsho thiab PTFE ua haujlwm zoo. Rau 260 mus rau 600 ° C, xav txog mica gaskets, ceramic fiber, los yog high-temperature phenolic laminates. Tshaj li 600 degrees C, kev sib cais ntawm cov hlau (siv cov khoom sib txuas nruab nrab) lossis ua tiav cov khoom hloov kho rau tib tsev neeg hlau yog tib txoj kev xaiv. Nco ntsoov xyuas cov khoom sib cais qhov ntsuas kub thiab tshuaj lom neeg sib xyaw nrog cov txheej txheem kua.
