Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175 / ISO 15156-2
- NORSOK M-650 Qualified
- API 6A Certified
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Super Duplex 2507 in Chemical Processing
Super Duplex 2507 (UNS S32750 / EN 1.4410) holds an important corner of the chemical-process material map: dilute hydrochloric acid (HCl), dilute sulphuric acid (H2SO4), hydrofluoric acid (HF) at low concentration and temperature, mixed-acid pickling baths, and chloride-laden organic streams. PREN above 41 and CPT above 50 degrees Celsius per ASTM G48 Method E let the alloy run where 316L pits within hours and where 904L starts to lose ground. Iso-corrosion charts vs 316L and 6Mo set the boundaries clearly.
TorqBolt supplies 2507 plate, pipe, fittings, flanges, fasteners, and forgings to chemical-process EPCs and operators with EN 10204 Type 3.1 mill test certificates as standard, Type 3.2 third-party-witnessed available where the project specification calls for it.
Why Super Duplex 2507 in Chemical Processing
Chemical-process service drivers:
- Dilute mineral acid resistance at low to moderate concentration and temperature (HCl, H2SO4, HF). 2507 holds up where 316L fails and where 904L is borderline.
- Chloride pitting and crevice resistance in chloride-contaminated organic streams (vinyl chloride monomer, ethylene dichloride, chlorinated solvents) and in cooling-water side of heat exchangers where chloride is concentrated by evaporation.
- Chloride stress corrosion cracking resistance in process streams where austenitic 304L / 316L would crack within months.
- Mechanical strength margin at 550 MPa minimum yield, roughly twice 316L. Vessel wall reduction on large columns and reactor shells.
- Cost vs Hastelloy C-276 / C-22. 2507 is 50 to 70 percent cheaper than nickel-base CRA and covers a useful corner of the iso-corrosion map.
Super Duplex 2507 Chemical Process Design Data
| Parameter | Value | Reference |
|---|---|---|
| PREN | 41 to 43 | Cr + 3.3 times Mo + 16 times N |
| CPT (ASTM G48 Method E) | Greater than 50 degrees Celsius | ASTM G48-11 |
| 10 percent H2SO4 iso-corrosion limit | Acceptable below about 60 degrees Celsius (less than 0.1 mm/yr) | Producer iso-corrosion charts |
| Dilute HCl (1 percent) iso-corrosion limit | Acceptable below about 40 degrees Celsius | Producer iso-corrosion charts |
| HF (5 percent) iso-corrosion limit | Acceptable below about 40 degrees Celsius | Producer iso-corrosion charts |
| Maximum continuous service temperature | 250 degrees Celsius (sigma-phase risk above 300) | NORSOK M-630 |
| Hardness limit (sour and acid service) | 28 HRC max | NACE MR0175 / ISO 15156-3 |
| Ferrite content | 35 to 55 percent (base), 35 to 65 percent (weld) | NORSOK M-630 |
Iso-corrosion limits above are typical and indicative. Always confirm against the mill producer iso-corrosion chart for the specific acid concentration, temperature, aeration, contaminants, and flow regime of the application before final material selection.
Where Super Duplex 2507 Is Specified in Chemical Processing
- Heat exchanger tubesheets and channel covers on chloride-laden cooling water and process duties. 2507 plate to ASTM A240, forgings to ASTM A182 F53.
- Reactor liners and clad reactor shells in chloride-contaminated organic and aqueous service. Cladding via roll-bond, weld-overlay, or solid construction depending on size.
- Distillation column trays, downcomers, and packing supports in chloride-contaminated organic distillation (chloromethanes, vinyl chloride monomer, ethylene dichloride).
- Pickling line tanks and piping in steel, copper, and aluminium mills. Mixed acid (HNO3 / HF) pickling at low concentration.
- Pump trims, valve trims, and pressure-vessel internals in dilute H2SO4 cooling-tower side-stream filters and dilute HCl regeneration systems.
- Phosphoric acid evaporators at low chloride and moderate temperature, where 904L is marginal.
- Caustic chloride brine cells in chlor-alkali plants on the brine side (not the chlorine side).
- Bleach plant pre-tower piping in pulp and paper (covered separately at the pulp and paper page).
- Crystalliser bodies and pumps in salt and sodium-sulphate recovery from caustic-process bleed streams.
Iso-Corrosion Comparison: 2507 vs 316L vs 6Mo
| Service | 316L Limit | 904L Limit | 2507 Limit | 6Mo Limit | Hastelloy C-276 Limit |
|---|---|---|---|---|---|
| 10 percent H2SO4 (aerated) | 20 degrees Celsius | 40 degrees Celsius | 60 degrees Celsius | 80 degrees Celsius | Greater than 100 degrees Celsius |
| 1 percent HCl (aerated) | Pits at all temperatures | 30 degrees Celsius | 40 degrees Celsius | 60 degrees Celsius | Greater than 80 degrees Celsius |
| 5 percent HF (aerated) | Pits at all temperatures | 30 degrees Celsius | 40 degrees Celsius | 50 degrees Celsius | Greater than 70 degrees Celsius |
| NaOH 50 percent | Below 100 degrees Celsius | Below 120 degrees Celsius | Below 80 degrees Celsius (caustic SCC risk above) | Below 100 degrees Celsius | Greater than 130 degrees Celsius |
| Phosphoric acid 75 percent (with Cl) | Pits | Borderline | Acceptable below 60 degrees Celsius | Acceptable below 80 degrees Celsius | Acceptable below 100 degrees Celsius |
Limits above are indicative for low-chloride, low-impurity feed at the stated concentration. Dissolved oxygen, contaminants (Cl, F, oxidising salts), velocity, and surface finish all shift the boundaries. Confirm against the mill producer iso-corrosion chart and, for critical duty, run a coupon test in the actual process stream.
Super Duplex 2507 Installation Notes for Chemical Processing
- Welding per NORSOK M-601 or AWS D1.6 with filler ER2594 (overmatching) for acid duty; heat input 0.5 to 2.5 kJ per millimetre, interpass below 150 degrees Celsius. Argon plus 2 to 5 percent nitrogen shielding for GTAW root.
- Pickling and passivation per ASTM A380 after fabrication: 20 percent nitric plus 5 percent HF, then citric or nitric passivation. Iron contamination from carbon-steel tools causes service pitting initiation.
- Cladding for large reactors and columns: roll-bond cladding (2507 + carbon-steel backer) is common where solid 2507 is uneconomic. Weld overlay (ER2594) is an alternative for repair and small areas.
- Crevice management at gasketed flanges. Spiral-wound CG gaskets with PTFE or graphite fill minimise crevice geometry vs flat-sheet rubber.
- Hydrotest with low-chloride water (less than 30 ppm chloride per ASTM A380), drain and dry within 24 hours.
- Bolting per ASTM A1082 / API 20F in matching S32750. PTFE thread lubricant on assembly.
- NDT per ASME V or NORSOK M-501: ferrite count per ASTM E562, ASTM A923 Methods A and B for sigma-phase screening on critical heats.
Recommended TorqBolt 2507 Products for Chemical Processing
- 2507 pipe: ASTM A790 seamless and welded
- 2507 fittings: ASTM A815 WP-S32750 buttweld
- 2507 flanges: ASTM A182 F53 weld neck and blind
- 2507 stud bolts: ASTM A1082 / API 20F for vessel and flange connections
- 2507 heavy hex nuts: ASTM A1082 in matching S32750
- 2507 plate, bar, forgings: ASTM A240 / A479 / A182 F53 for tanks, columns, tubesheets
Related Application Pages
- Pulp and paper: bleach plant chlorine dioxide service
- FGD: wet flue gas desulfurization
- Desalination: MSF, MED, RO brine
- Seawater applications: sea-chest, fire-water
- Oil and gas: wellheads, manifolds
Super Duplex 2507 Chemical Processing FAQ
Is 2507 acceptable for 10 percent H2SO4 service?
Below about 60 degrees Celsius the corrosion rate of 2507 in 10 percent aerated H2SO4 stays under 0.1 mm/yr per typical mill iso-corrosion charts. Above that temperature, the rate climbs and 904L or 6Mo become more economic. Always confirm the specific service against the mill producer iso-corrosion chart, since impurities (Cl, F, oxidising salts) shift the boundaries materially.
Can 2507 handle dilute HCl?
Yes, at low concentration (around 1 percent) and low temperature (below about 40 degrees Celsius), 2507 stays inside the 0.1 mm/yr corrosion-rate envelope. At higher concentration or temperature, the next step up is 6Mo, then Hastelloy C-276 / C-22. The boundary moves with chloride concentration, dissolved oxygen, and aeration; coupon tests in the actual stream are recommended for borderline duty.
What about HF service?
2507 handles dilute HF (around 5 percent) below 40 degrees Celsius. Mixed-acid pickling baths (HNO3 plus HF) at low HF concentration are a common 2507 application. Above 40 degrees Celsius or above 5 percent HF, the rate climbs and 6Mo or Hastelloy C-276 / C-22 are the next step up. Anhydrous HF is outside the 2507 envelope.
Where does 2507 fail in chemical service?
Three regimes drive 2507 failure: hot concentrated chloride (above CPT), reducing acids at temperature (concentrated H2SO4 above 60 degrees Celsius, concentrated HCl), and caustic SCC in hot 50 percent NaOH above 80 degrees Celsius. At those conditions, the next alloy up is 6Mo for moderate severity and Hastelloy C-276 / C-22 for the most severe duty.
Can 2507 be roll-bond clad to carbon-steel reactor shells?
Yes. Roll-bond cladding (2507 plate hot-bonded to carbon-steel backer) is the standard construction for large chemical reactors and columns where solid 2507 is uneconomic. Bond-strength qualification per ASTM A263 / A264 / A265 (analogous procedures), shear test on every plate, ultrasonic disbond inspection. Cladding thickness typically 3 to 6 mm depending on corrosion allowance.
What welding filler is correct for 2507 in acid service?
ER2594 (overmatching, slightly higher PREN than the base) per AWS A5.9 is the standard pick for acid duty. ER2553 (matching) is acceptable for less aggressive applications. Heat input 0.5 to 2.5 kJ per millimetre, interpass below 150 degrees Celsius. Argon plus 2 to 5 percent nitrogen shielding for GTAW root pass to maintain weld-metal nitrogen.
How do I choose between 2507 and Hastelloy C-276 for a chemical service?
Run the iso-corrosion chart at the actual concentration and temperature for both alloys. If 2507 sits inside the 0.1 mm/yr envelope with margin, it is the correct economic choice (50 to 70 percent cheaper than C-276). If 2507 is borderline or outside the envelope, C-276 is the safer pick. For mixed-acid or oxidising service with chloride present, C-276 typically wins; for dilute single acids without strong oxidisers at moderate temperature, 2507 wins.
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