Surface Treatments
Certifications
- ISO 9001:2015
- NORSOK M-650
- NACE MR0175
- ISO 15156-3
- PED 2014/68/EC
- EN 10204 type 3.2
- AD 2000 W2/W7/W10
Ferralium 255 in Chemical Processing
Reducing-acid, brine, sulphuric, hydrochloric, and chloride-bearing chemical service for the Cu-bearing super duplex grade
The 2 percent copper addition that distinguishes Ferralium 255 (UNS S32550) from Cu-free super duplex grades like 2507 (S32750) and Zeron 100 (S32760) is the metallurgical differentiator that opens chemical-processing service. Copper improves the alloy's resistance in reducing acids (sulphuric, hydrochloric, phosphoric, and the chloride-bearing organic acids) where the Cu-free super duplex grades suffer general corrosion. The cost premium of Ferralium 255 over standard duplex 22Cr is justified specifically by this copper benefit in the wet-process chemical industries: phosphoric-acid evaporators (where H2SO4 contamination is unavoidable), kraft-pulp digesters under upset conditions, dilute-HCl pickling lines, and the bottoms section of refinery vacuum towers handling chloride-stripped feed.
Acid-Service Envelope
| Acid | Concentration | Temperature | Ferralium 255 acceptance |
|---|---|---|---|
| Sulphuric acid (H2SO4) | 0 to 30% | up to 80 °C | Acceptable; corrosion rate ≤ 0.1 mm/yr |
| Sulphuric acid | 30 to 70% | up to 50 °C | Marginal; consider 2507 or nickel-alloy |
| Sulphuric acid | > 70% | any | Not acceptable; specify alloy 20 / Inconel 825 |
| Hydrochloric acid (HCl) | 0 to 1.5% | up to 40 °C | Acceptable; corrosion rate ≤ 0.1 mm/yr |
| Hydrochloric acid | 1.5 to 5% | up to 25 °C | Marginal; consider C-276 |
| Phosphoric acid (H3PO4) wet-process | up to 54% P2O5 | up to 90 °C | Acceptable with chloride < 200 ppm; the Cu benefit shows here |
| Sodium hydroxide (NaOH) | up to 50% | up to 100 °C | Acceptable; super duplex routinely outperforms 316L in caustic |
| Acetic, formic, citric organic acids | any concentration | up to boiling | Acceptable; preferred over 316L for chloride-contaminated organic acids |
| Chlorinated brine (NaCl, CaCl2, MgCl2) | up to saturation | up to 232 °C (NACE limit) | Acceptable; the prime use case |
Typical Chemical-Plant Components
- Phosphoric-acid evaporator tubes and tube-sheets (the headline application for Cu-bearing super duplex)
- Kraft-pulp digester white-liquor and brown-stock pump components
- Pickling-line racks and grids for hot-dip galvanising plant
- Hydrochloric-acid regeneration plant heat-exchanger components
- Brine-handling pump casings and impellers in chlor-alkali plant
- Sulphuric-acid plant absorber-tower internals (acceptance limited by concentration / temperature, see table)
- Citric / formic / acetic acid storage tank linings where chloride contamination is intermittent
When to Escalate Beyond Ferralium 255
Above the acid-service envelope, the escalation path is to nickel-base alloys: alloy 20 (UNS N08020) for higher concentrations of sulphuric acid, Inconel 825 (UNS N08825) for sulphuric and phosphoric mixtures with chloride, Inconel 625 (UNS N06625) for the broadest envelope of acid plus chloride plus elevated temperature, Hastelloy C-276 (UNS N10276) for severe acid-plus-chloride service. See the Ferralium 255 vs Inconel 625 comparison page for the cost-vs-corrosion-rate trade-off.
Related Pages
- Ferralium 255 chemical composition (the 2% Cu source)
- Ferralium 255 vs Inconel 625 (escalation route)
- Ferralium 255 vs 2507 (the Cu benefit explained)
- Ferralium 255 pipe
- Ferralium 255 fittings
Need Ferralium 255 for chemical processing service? Email info@torqbolt.com or WhatsApp +91-22-66157017 with form, dimensions, quantity, ASTM/EN spec, MTC level (3.1 / 3.2). NACE MR0175 sour-service stamp on every heat. NORSOK M-650 QTR on request. Per-heat EN 10204 type 3.2 MTC included with every consignment.
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