904L vs 316L Stainless Hlau Sulfuric Acid Resistance Showdown

Thaum sulfuric acid nkag mus rau hauv qhov sib npaug, kev xaiv ntawm stainless hlau qib tsis yog ib qho teeb meem ntawm kev nyiam - nws tuaj yeem txiav txim siab seb cov nroj tsuag puas muaj kev ntseeg siab rau nees nkaum xyoo lossis raug kev puas tsuaj rau hauv nees nkaum lub hlis. Kab lus no muab cov ntaub ntawv nruj, cov ntaub ntawv -tsav kev sib piv ntawm904L (UNS N08904 / EN 1.4539)thiab316L (UNS S31603 / EN 1.4404), ob qhov kev soj ntsuam ntau tshaj plaws thaum cov engineers ntsib acid-muaj cov txheej txheem ib puag ncig

. 904L vs 316L Stainless Steel

Hauv qab -Line Findings:

904L yog qhov ua tau zoo tshaj plaws rau 316L hauv sulfuric acid kev pabcuam thoob plaws yuav luag txhua qhov kev xav tau thiab qhov kub thiab txias qhov twg 316L tseem muaj txiaj ntsig zoo.

316L yog tus nqi - qib tus qauv zoo rau kev siv dav dav - lub hom phiaj kev siv qhov twg sulfuric acid tsis tuaj lossis tam sim no tsuas yog nyob rau hauv qhov muaj pes tsawg leeg ntawm qhov kub thiab txias.

Rau nruab nrab-rau- cov kua qaub hnyav, tus nqi pib ntau dua ntawm 904L yog qhov tsis tu ncua los ntawm kev txo qis qis, cov cuab yeej siv tau ntev, thiab txo qis kev poob qis.

Sulfuric acid (H₂SO₄) yog lub ntiaj teb cov khoom lag luam dav dav, siv hauv kev tsim cov chiv, hlau pickling, roj av refining, roj teeb ntau lawm, thiab ntau yam txheej txheem. Kev nkag siab yog vim li cas nws thiaj li corrosive rau hlau - thiab yog vim li cas alloy xaiv tseem ceeb heev - yog ib qho tseem ceeb ntsiab lus rau txhua tus engineer ua hauj lwm nyob rau hauv cov lag luam.

Vim li cas H₂SO₄ Tshwj xeeb yog Corrosive

Sulfuric acid tawm tsam hlau los ntawm ob lub hauv paus mechanisms: ncaj qha acid nres (hydrogen evolution), uas dominates ntawm concentrations hauv qab no kwv yees li 40%, thiab ib tug passive - zaj duab xis- dissolving mechanism ntawm intermediate concentrations. Ntawm qhov siab heev (ntau tshaj 93%), cov kua qaub ua rau lub cev qhuav dej thiab ua tau ib txheej tiv thaiv ntawm qee cov alloys - tab sis qhov no yog qhov nqaim thiab kub heev - qhov rais rhiab heev.

Rau cov tswv yim engineering, qhov chaw txaus ntshai tshaj plaws rau cov hlau tsis muaj steel yog 5-70% concentration ntau ntawm qhov kub siab tshaj 40 degree. Nyob rau hauv no ntau yam, tag nrho cov qauv austenitic qib nrog rau 316L muaj kev cuam tshuam cov zaj duab xis sai sai, ua rau kom ceev ceev corrosion.

Lub luag haujlwm ntawm Alloying Elements

Peb cov ntsiab lus alloying tseem ceeb heev rau H₂SO₄ tsis kam nyob rau hauv austenitic stainless hlau: molybdenum (Mo), npib tsib xee (Ni), thiab tooj liab (Cu). Kev nkag siab txog lawv lub luag haujlwm ua rau 904L vs 316L kev ua tau zoo sib txawv tam sim ntawd.

Molybdenum (Mo): Mo stabilizes cov zaj duab xis passive hauv kev txo cov kua qaub ib puag ncig. 904L muaj 4-5% Mo piv rau 2-3% hauv 316L. Qhov sib txawv no kwv yees ob npaug ntawm cov yeeb yaj kiab passive hauv sulfuric acid.

Nickel (Ni): Ni txo tus nqi ntawm kev ua kom nquag plias thiab hloov cov hlau mus rau qhov tsis muaj zog hauv kev txo cov xov xwm . 904L's 23-28% Ni cov ntsiab lus (piv rau 10-14% hauv 316L) yog kab tias tus tsav tsheb loj tshaj plaws ntawm nws cov kua qaub ua kom zoo dua.

Copper (Cu): Kev txhob txwm sib ntxiv ntawm 1-2% Cu hauv 904L yog tsim tshwj xeeb los txo tus nqi corrosion hauv dilute - rau - nruab nrab H₂SO₄. 316L tsis muaj tooj liab. Qhov no yog ib qho kev txiav txim siab feem ntau sib txawv ntawm ob qib.

Cov lus sib xyaw hauv qab no yog qhov pib rau kev nkag siab txhua qhov kev ua tau zoo ntawm ob qib no. Tag nrho cov nqi yog raws li cov ntaub ntawv specifications.

Table 1: Chemical Composition - 316L vs 904L (Txhua tus nqi hauv qhov hnyav %)

Element	316L Min	316L Max	904l ua	904l ua	Chav tsev
Chromium (Cr)	16.0	18.0	19.0	23.0	%
Nickel (Ni)	10.0	14.0	23.0	28.0	%
Molybdenum (hli)	2.0	3.0	4.0	5.0	%
Copper (Cu)	-	-	1.0	2.0	%
Manganese (Mn)	-	2.00	-	2.00	%
Silicon (Si)	-	0.75	-	1.00	%
Cov pa roj carbon (C)	-	0.030	-	0.020	%
Nitrogen (N)	-	0.10	-	0.10	%
Sulfur (S)	-	0.030	-	0.035	%
Phosphorus (P)	-	0.045	-	0.045	%
Hlau (Fe)	Tshuav	Tshuav	Tshuav	Tshuav	-

Peb Qhov Tseem Ceeb Ntawm Qhov Sib Txawv

Nickel Differential (+13–14% ntau dua hauv 904L): Nickel yog tib lub ntsiab lus tseem ceeb tshaj plaws rau kev txo qis kev sib cais hauv kev txo cov kua qaub. Qhov 13-14 feem pua ntawm qhov sib txawv ntawm cov ntsiab lus npib tsib xee ntawm 904L thiab 316L yog lub luag haujlwm rau feem ntau ntawm 904L qhov kev ua tau zoo dua corrosion.

Molybdenum Differential (+2% ntau hauv 904L): Ib qho ntxiv 2% molybdenum hauv 904L stabilizes cov zaj duab xis passive hauv acidic. Thaum qhov no tuaj yeem tshwm sim me me, Mo cov txiaj ntsig ntawm kev ruaj ntseg zaj duab xis tsis yog -linear thiab muab cov txiaj ntsig tsis sib xws hauv cov cheeb tsam acidic.

Copper Ntxiv (1-2% hauv 904L, tsis tuaj hauv 316L): Qhov no yog qhov tsis txaus siab tshaj qhov sib txawv. tooj liab ncaj qha txo tus nqi ntawm hydrogen evolution corrosion nyob rau hauv sulfuric acid los ntawm kev ua raws li ib tug cathodic inhibitor . 316L tsis muaj tooj liab kiag li, thiab tsis muaj pes tsawg ntawm lwm yam alloying yuav them rau nws tsis nyob rau hauv sulfuric acid kev pab cuam.

Table 2: Mechanical Properties - 316L vs 904L

Khoom	316l qw.	316L TSI	904l qw.	904l ua
Tensile zog (MPa)	Ntau dua lossis sib npaug rau 485	~560	Ntau dua lossis sib npaug li 490	~540
0.2% Tawm Zog (MPa)	Ntau dua lossis sib npaug li 170	~220	Ntau tshaj los yog sib npaug rau 220	~260
Elongation ntawm Break (%)	Ntau dua lossis sib npaug li 40	~50	Ntau dua lossis sib npaug li 35	~42
Hardness (HB)	Tsawg dua lossis sib npaug li 217	~150	Tsawg dua los yog sib npaug li 200	~170
Impact Toughness (J, -196 degree)	Zoo	~80–120	Zoo heev	~100–140
Modulus ntawm Elasticity (GPa)	~193	193	~196	196
Qhov ceev (g / cm³)	7.99	7.99	8.00	8.00

904L muaj me ntsis siab dua qhov kev tawm dag zog tsawg dua 316L, feem ntau vim nws muaj ntau cov npib tsib xee thiab me ntsis ntxiv nitrogen. Ob qib muab ductility zoo heev thiab toughness ntawm txhua qhov kub thiab txias nrog rau cov mob cryogenic. Rau feem ntau cov txheej txheem siv tshuaj, cov cuab yeej cuab tam sib txawv yog qhov thib ob rau kev ua haujlwm corrosion hauv kev txiav txim siab xaiv cov khoom.

Tshooj lus no nthuav tawm cov ntaub ntawv tseem ceeb tshaj plaws hauv kab lus no. Kev sib piv tus nqi corrosion nyob rau hauv ib tug matrix ntawm H₂SO₄ concentrations thiab kub yog lub hauv paus ntsiab lus rau kev xaiv cov khoom nyob rau hauv acid kev pab cuam. Tag nrho cov nqi yog nyob rau hauv millimeters ib xyoo (mm/y); tus nqi qis dua 0.1 mm / y feem ntau suav hais tias yog siv tau rau kev pabcuam ntev -.

Table 3: Corrosion Rates nyob rau hauv Sulfuric Acid - 316L vs 904L (mm/xyoo)

H₂SO₄ Conc. (wt%)	Temp. (degree)	316L tus nqi (mm / y)	904L tus nqi (mm / y)	Kev txhim kho Factor	904l ua	316L Suitability
1–5	20	0.05–0.10	0.01–0.02	~5×	Zoo heev	Zoo heev
1–5	60	0.20–0.50	0.03–0.08	~6×	Zoo heev	Txais tau
5–20	20	0.50–1.50	0.05–0.15	~10×	Zoo heev	Marginal
5–20	60	1.50–5.00	0.10–0.40	~12×	Zoo	Tsis haum
20–40	20	3.00–8.00	0.20–0.80	~10×	Zoo – Txais	Tsis haum
20–40	60	>10	0.50–2.00	>5×	Marginal	Tsis haum
40–70	20	>10	0.80–3.00	>3×	Marginal	Tsis haum
40–70	60	>>10	2.00–8.00	-	Tsis haum	Tsis haum
70–90	20	>>10	>5.00	-	Tsis haum	Tsis haum
90–98	20	>>10	>5.00	-	Tsis haum	Tsis haum

Txhais cov ntaub ntawv Corrosion Rate

Cov ntaub ntawv nyob rau hauv Table 3 qhia ib tug meej, zoo ib yam dab neeg: 904L outperforms 316L los ntawm ib yam ntawm 5 mus rau 12 lub sij hawm nyob rau hauv cov feem ntau industrially sulfuric acid tej yam kev mob (1-40% concentration, 20-60℃kev khiav hauj lwm kub). Qhov tseem ceeb tshaj, rau qhov siab tshaj 5% ntawm qhov kub siab tshaj 40 degree, 316L feem ntau tshaj li 1.0 mm / y pib - ua rau nws ua haujlwm tsis zoo, tsis hais txog kev tsim qauv.

Ntawm qhov siab tshaj 40–70%, tsis muaj qib tsis muaj kev tiv thaiv txaus nyob rau lub sijhawm ntev - kev pabcuam. Cov kws ua haujlwm ntsib cov concentrated sulfuric acid (ntau tshaj 70%) yuav tsum ntsuas cov khoom tshwj xeeb xws li Alloy 20 (UNS N08020), Hastelloy B-3 (UNS N10675), lossis high-silicon cam khwb cia hlau, uas yog tsim tshwj xeeb rau cov concentrated H₂SO₄ kev pabcuam.

Sulfuric acid tsis tshua muaj tsuas yog hom corrosive nyob rau hauv cov txheej txheem kev lag luam. Cov lus hauv qab no muab kev pom dav dav ntawm ob qib no ua tau zoo nyob rau txhua qhov kev txhim kho corrosion loj thiab cov kua qaub.

Table 4: Multi-Ib puag ncig Corrosion Resistance - 316L vs 904L

Corrosion Mechanism / Ib puag ncig	904l ua	Kev ntsuas	316L Kev ua haujlwm siab	Kev ntsuas
Dilute H₂SO₄ (<10%, ambient)	Zoo heev	★★★★★	Zoo	★★★☆☆
Dilute H₂SO₄ (<10%, 60°C)	Zoo heev	★★★★☆	Marginal	★★☆☆☆
Conc. H₂SO₄ (40–70%, ambient)	Marginal	★★☆☆☆	Tsis haum	★☆☆☆☆
Phosphoric Acid (H₃PO₄)	Zoo heev	★★★★★	Zoo	★★★☆☆
Acetic Acid (CH₃COOH)	Zoo heev	★★★★★	Zoo heev	★★★★☆
Hydrochloric acid (HCl)	pluag	★★☆☆☆	pluag	★☆☆☆☆
Chloride Pitting (Cl⁻ env.)	Zoo heev	★★★★☆	Zoo	★★★☆☆
Crevice Corrosion (seawater)	Zoo	★★★☆☆	Marginal	★★☆☆☆
Intergranular Corrosion	Zoo heev	★★★★★	Zoo heev	★★★★☆
Kev ntxhov siab Corrosion Cracking (SCC)	Zoo heev	★★★★☆	Marginal	★★☆☆☆
Oxidising Acids (HNO₃)	Zoo	★★★☆☆	Zoo heev	★★★★☆

Nitric Acid: Ib cheeb tsam uas 316L muaj ntug

Nitric acid (HNO₃) yog ib qho oxidising acid, thiab nyob rau hauv oxidising acid ib puag ncig, chromium cov ntsiab lus dominates qhov kev tiv thaiv mechanism. Ob qib muaj cov qib chromium zoo sib xws (16–18% hauv 316L; 19–23% hauv 904L), tab sis 316L cov molybdenum qis dua ua rau nws zoo dua me ntsis rau cov kev pabcuam HNO₃ vim Mo tuaj yeem ua rau muaj kev puas tsuaj rau qhov chaw oxidising heev. Txawm li cas los xij, qhov no yog qhov tshwj xeeb nqaim - ib qho txheej txheem sib xyaw HNO₃ nrog HCl lossis H₂SO₄ (cov kua qaub sib xyaw) tam sim hloov qhov zoo rov qab rau 904L.

Chloride Resistance: Pitting thiab Crevice Corrosion

Tus Pitting Resistance Equivalent Number (PREN) ntsuas qhov tsis kam rau chloride -induced pitting. 904L ua tiav PREN ntawm kwv yees li 32–36 piv rau 316L's 23–27. Qhov sib txawv no yog qhov tseem ceeb hauv txhua daim ntawv thov uas chloride ions co- muaj nyob nrog sulfuric acid - ib qho xwm txheej nyob rau hauv cov txheej txheem kev lag luam, cov pa roj paug ib puag ncig, thiab daim ntawv thov kev kho dej.

Table 5: Lub cev thiab Thermal Properties - 316L vs 904L

Khoom	316L	904L
Melting Range (zeeg)	1375–1400	1300–1390
Qhov ceev (g / cm³)	7.99	8.00
Thermal conductivity (W / m · K, 20 degree)	13.4	12.0
Cov. Thermal Expansion (µm / m· degree)	16.0 (20-100 degree)	15.3 (20-100 degree)
Lub peev xwm kub tshwj xeeb (J / kg·K)	500	450
Hluav taws xob tiv thaiv (µΩ·m)	0.74	0.95
Sib nqus permeability (annealed)	~1.005	~1.003
Max Service Temp. - Oxidising (degree)	~870	~1050
Max Service Temp. -Aqueous (degree)	~300	~300

Ob qib sib qhia dav dav zoo sib xws lub cev thiab thermal zog, raws li kev cia siab rau austenitic alloys nrog rau qhov sib piv tag nrho cov alloying qib. Lub thermal expansion me ntsis ntawm 316L tej zaum yuav muaj feem xyuam rau hauv lub tshav kub exchanger tube tsim tab sis tsis tshua muaj kev xaiv cov khoom siv. Ob qib tsis yog- sib nqus nyob rau hauv cov mob annealed, ua rau lawv haum rau cov ntawv thov uas tsis tshua muaj hlau nplaum permeability (xws li, MRI chaw tsim kho, qee yam cuab yeej).

Cov qauv tsim kom raug yog qhov tseem ceeb rau kev yuav khoom, kev tshuaj xyuas zoo, thiab kev ua raws cai. Cov lus hauv qab no suav tag nrho cov txheej txheem tsim npe thoob ntiaj teb loj rau ob qib.

Applicable Standards and International Certifications

Table 6: Cov Qauv thiab Cov Qauv - 316L vs 904L

Txheem lub cev	316L npe	904l npe	Scope / Sau ntawv
ASTM	S31603	N08904	Phaj, Sheet, Sawb, Bar, Yeeb Nkab, Tube
EN / DIN	1.4404	1.4539	European cov ntaub ntawv cov khoom
UNS	S31603	N08904	Unified Numbering System
ASME	SA-240/SA-312	SA-240/SA-312	Cov Khoom Siv Hluav Taws Xob, Boilers, Piping
ISO	ISO 15156-3	ISO 15156-3	Qab zib -kev pabcuam (H₂S ib puag ncig)
NCEES / AMPP	MR0175 ua raws	MR0175 ua raws	Kev pabcuam roj & roj corrosion
PEB (EU)	2014/68/EU	2014/68/EU	Cov Lus Qhia Cov Khoom Siv Siab
FDA (khoom noj khoom haus / tshuaj)	Txais	Txais	Nto tiav Ra Tsawg dua lossis sib npaug rau 0.8 µm raug

Ob qib tau them tag nrho raws li ASME, ASTM, thiab EN lub luag haujlwm rau cov hlab ntsha siab, cov khoom siv hluav taws xob, thiab cov kav dej. Rau FDA- tswj cov ntawv thov tshuaj thiab zaub mov, ob qib raug lees txais, nrog 316L yog qhov ze - thoob ntiaj teb vim nws cov ntaub ntawv tsim tawm, tus nqi qis, thiab cov saw hlau thoob ntiaj teb.

Tus nqi ntawm cov khoom siv feem ntau yog qhov kev txiav txim siab pom tam sim ntawd, tab sis cov nqi ntawm lub neej - uas suav nrog kev saib xyuas, hloov, thiab kev tsim khoom poob qis - yuav luag txhua zaus nyiam qhov siab dua - kev ua tau zoo alloy hauv cov kua qaub. Cov lus hauv qab no nthuav qhia cov kev lag luam tseem ceeb thiab kev tsim khoom.

Table 7: Nqi, Muaj, thiab Fabrication - 316L vs 904L

Qhov xwm txheej	316L	904L
Tus nqi ntawm cov khoom siv sib txheeb (Plate)	Lub hauv paus (1.0 ×)	~ 1.8–2.5 × (Ni, Mo)
Thawj Tus Nqi Tsav Tsheb	Ni (10–14%), Mo (2–3%)	Ni (23–28%), Mo (4–5%), Cu
Ntiaj teb no muaj nyob	Ubiquitous - tag nrho cov mills	Muaj dav - tshwj xeeb
Hom Lub Sijhawm Lead (Plate)	1-4 lub lis piam	3-8 lub lis piam
Weldability	Zoo heev (ER316L muab tub lim)	Zoo heev (ER385 muab tub lim)
Machineability	Zoo	Zoo rau nruab nrab
Fabrication Complexity	Tsawg - yooj yim rau daim ntawv / vuam	Nruab nrab - standard austenitic
Nto Finish Options	Tag nrho cov txheej txheem tiav	Tag nrho cov txheej txheem tiav
Mill daim ntawv pov thawj (EN 10204)	3.1 ib txwm muaj	3.1 / 3.2 muaj

Vuam Cov Lus Qhia

Kev xaiv hlau muab tub lim raug yog qhov tseem ceeb rau kev tswj xyuas corrosion hauv thaj tsam weld:

316L: AWS ER316L muab tub lim (los yog txuam cov electrode E316L). Tsawg cua sov input. Tsis xav tau preheating. Cov txheej txheem dav dav ua rau 316L qhov yooj yim tshaj plaws fabricated stainless qib thoob ntiaj teb.

904L: AWS ER385 filler metal (or Avesta 904L / Sandvik 27.31.4.LCu type). Me ntsis nruj dua interpass kub tswj tau pom zoo. Tag nrho cov tshuaj anneal post-weld tsis yog yuav tsum tau tab sis pom zoo rau cov kev pabcuam nruj tshaj plaws. Purge nrog inert roj rau cov yeeb nkab hauv paus hla.

Ob qib: Tsis tas yuav tsum tau preheating. Siv stainless- txhuam txhuam hlau thiab cov log sib tsoo tshwj xeeb. Ntxuav qhov chaw kom huv si kom tshem tawm cov kab mob hlau thiab tiv thaiv tsis muaj hlau corrosion.

Cov lus xaiv nram qab no muab cov engineers, procurement specialists, thiab plant managers nrog ncaj qha, pov thawj -raws li kev taw qhia ntawm qib twg los qhia rau cov kev pab cuam.

Table 8: Daim Ntawv Thov thiab Kev Xaiv Kev Lag Luam Phau Ntawv Qhia - 316L vs 904L

Daim Ntawv Thov / Ib puag ncig	316L	904L	Tseem ceeb Technical Rational
Dilute H₂SO₄ cia (<5%, ambient)	Siv tau	Nyiam	904L's Cu + Mo ua ke ua rau txo qis corrosion
H₂SO₄ piping systems (<20%, <60°C)	Marginal	Nyiam	316L corrosion tus nqi siab tshaj 1 mm / y ntawm cov xwm txheej no
H₂SO₄ neutralization / txhuam	Siv tau	Nyiam	Mixed acid / dej ntws nyiam 904L txoj kev dav dua
Phosphoric acid (H₃PO₄) ua	Siv tau	Nyiam	Ob leeg ua tau zoo; 904L zoo tshaj ntawm qhov kub siab
Cov txheej txheem acetic acid	Nyiam	Siv tau	316L txaus ntawm qhov kub thiab txias; txuag nqi vs 904L rau lub luag haujlwm me me
Nitric acid (HNO₃).	Nyiam	Siv tau	Oxidising acid nyiam Cr; 316L nqi -zoo ntawm no
Pharmaceutical hlab ntsha & reactors	Nyiam	Siv tau	316L FDA- qauv; 904L tsuas yog cov txheej txheem xav tau nws
Kev ua zaub mov & dej haus	Nyiam	Siv tau	316L ua tau raws li tag nrho cov qauv kev tu cev ntawm tus nqi qis dua
Seawater txias / cua sov exchangers	Marginal	Nyiam	904L pitting kuj (PREN ~ 32) vs 316L's (~ 24)
Fertilizer cog - sulphate ntws	Tsis haum	Nyiam	Sov sulphate + chloride ua ke yuav tsum tau 904L
Roj & roj ntau lawm - kev pabcuam qaub	Siv tau	Nyiam	904L siab dua Ni txo qhov kev pheej hmoo ntawm SCC hauv H₂S ib puag ncig
Cryogenic / LNG cia	Nyiam	Siv tau	316L dav tsim nyog rau LNG; 904L tshaj - qhia ntawm no
Cov kav dej siv dav dav (tsis yog-acid)	Nyiam	Siv tau	316L muaj qhov sib npaug ntawm kev txuag nqi

Cov lus hauv qab no distills txhua qhov ntev ntawm qhov kev sib piv no rau hauv ib qho kev qhia luv luv.

Table 10: Kev sib piv cov ntsiab lus dav dav - 316L vs 904L

Dimension	904L	316L
UNS / EN npe	N08904 / 1.4539	S31603 / 1.4404
Cov ntsiab lus Nickel	23-28% (ntau dua)	10–14%
Molybdenum Cov ntsiab lus	4–5%	2–3%
Copper Ntxiv	1-2% (acid resistance boost)	Tsis muaj
PREN Tus nqi	~32–36	~23–27
H₂SO₄ Resistance	Superior nyob rau hauv cov concentrations	Txwv rau dilute / ambient
Corrosion Rate (<10% H₂SO₄)	5-12 × qis dua 316L	Lub hauv paus
SCC Resistance	Zoo heev (Nyob zoo)	Marginal
Seawater Resistance	Zoo	Marginal
Weldability	Zoo heev	Zoo heev
Tus nqi ntawm cov khoom siv txheeb ze	~ 1.8-2.5 × siab	Lub hauv paus
Ntiaj teb no muaj nyob	Muaj dav (tshwj xeeb)	Ubiquitous
Zoo tshaj plaws	Acid / tshuaj ua haujlwm	General / zaub mov / pharma