Ferralium 255


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Ferralium 255 – 1.4507,UNS S32550, F61

Ferralium® 255 – super duplex 4507 is a super duplex stainless steel supplied in the hot worked and annealed condition. It achieves higher strengths than most stainless steels and alternative corrosion resistant alloys, offering the potential to reduce section size and therefore weight and cost.

As a 25% Cr alloy, with significant additions of copper, Ferralium® 255 offers excellent corrosion resistance in a wide variety of corrosive chemicals including sulphuric, nitric and phosphoric acid. In seawater and other chloride containing environments it also provides outstanding resistance to pitting and crevice corrosion, with Critical Pitting Temperature exceeding 50°C. Excellent ductility and impact strength at both ambient and sub-zero temperatures combine with a high resistance to abrasion, erosion and cavitation erosion.

Listed in NACE MR 01 75 for sour service and having gained ASME Approval for Pressure Vessel applications, Ferralium® 255-SD50 is tested to the highest degree using tests designed to guarantee that the trade-marked product possesses high integrity, a correct phase balance and the absence of sigma and other deleterious phases.

S FERRALIUM 255 (UNS S32550) Description

Cr 25.5, Ni 5.5, Mo 3.4 C 0.04, Mn 1.5, Si 1.0, Fe Bal, N 0.175, S 0.030, Cu 2.00, P 0.040


Applications s32550, F61

FERRALIUM 255 is a cost effective alternative to materials such as the nickel alloys, 20 type alloys, brass and bronze. Marine environments have long been the domain of admiralty bronze. Alloy 255 is replacing admiralty bronze, and the nickel alloys, in offshore platforms, deck hardware, rudders and shafting.

Alloy 255 is also making inroads in “borderline” corrosion applications where the nickel alloys and high performance alloys have been used but may not have been absolutely necessary. In some instances, it has even been used to replace high performance Ni-Cr-Mo-F-Cu alloys in the phosphoric acid industry.

Valves, pumps, shafts, marine environments, Applications in down-hole, waste water, polycarbonate production, and demineralized water production.

Tensile Data

Mechanical Property Requirements
Ultimate Tensile Yield Strength (0.2% OS) Elong. R/A Hardness Brinell
Min 110 KSi 80 KSi 15%
Max 297
Min 760 MPa 550 MPa


Is Stronger Than Most Competitive Alloys
Alloy UNS Typical Tensile
Typical Yeild
Typical Elongation
Alloy 255 S32550 126 98 30
SUS316L S31603 81 42 50
NiCu400 N04400 78 31 50
20Cb-3 N08020 92 47 39
2205 Duplex S31803 112 75 32


  • Ferraliu255 – SD50 (Super Duplex 255)
  • 4507
  • ASTM A276/A476
  • UNS S32550

A182 F61Other Technical Data

Elongation Comparison
elongation Comparison
elongation Alloy 316SS Alloy 2205 Ferralium Alloy 255
40 25 15
Hardness Comparison
Wear Resistance Alloy 316SS Alloy 2205 Ferralium Alloy 255
Hardness RB80 RC21 RC28
Critical Pitting Temperature Comparison
Critical Pitting Temperature Alloy 316SS Alloy 2205 Ferralium Alloy 255
Degree C ASTM
G48-Method A
0 20 40
Pitting Potential – MV Comparison
Temperature Alloy 316SS Alloy 2205 Ferralium Alloy 255
50 °C 60 370 No Pitting
60 °C No Test No Test 110
60 °C No Test No Test 170
Critical Crevice Comparison
Critical Crevice Temperature Alloy 316SS Alloy 2205 Ferralium Alloy 255
Degree C ASTM
G48-Method B
(10% FE CL 6H 0)
-2.5 17.5 22.5
C Ring Stress Cracking Comparison
C Ring Stress Cracking Alloy 316SS Alloy 2205 Ferralium Alloy 255
80 Degree C Stressed to 100% Yield Strength, H2S
0.125 Bar, Sour Brine with 46,000 MG/L Chloride
Cracks Fine Cracks No Cracks
PREN No. Comparison
Resistance to Localized Corrosion Alloy 316SS Alloy 2205 Ferralium Alloy 255
PREN No. CR + 3.3(MO) + 16(N) 23.6 34.5 40
Corrosion Rates Comparison
Corrosion Rates MPY Alloy 316SS Alloy 2205 Ferralium Alloy 255
10% Sulfuric Boiling 855 206 40
65% Nitric Boiling 11 21 5
  • FERRALIUM® is a registered trademark of Langley Alloys LTD.