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25 Chrome: Duplex Stainless Steel

Common Names:

25CR, 2507, VM25

Alloy Group

Duplex Stainless Steel

Corrosion Resistance

Moderate

Yield Strength

65

—

160

Wall Tolerance

0.875

Density

0.281

PREN

35.83

—

45.65

Additional Documentation

Alloy Details

25 Chrome (UNS S31260), also known as 2507 Duplex or Chromium-25, is a cold-hardened duplex stainless steel designed for corrosion resistance in sweet (CO2) and mildly sour (H2S) environments with high chloride content, providing high strength up to 450°F.

Compared to 22 Chrome, 25 Chrome offers enhanced resistance to CO2, chlorides, pH variations, and elevated temperatures. This makes it suitable for use in deeper wells with high-pressure, high-temperature (HPHT) conditions, where pitting corrosion from high chloride concentrations is a concern. It is commonly used for downhole tubular components, casing, packers, and other subsurface equipment, and is often selected for critical Class VI well projects, such as those involving Carbon Capture, Utilization, and Storage (CCUS).

This alloy is classified under NACE MR0175/ISO15156 as a duplex stainless steel with a Pitting Resistance Equivalent Number (PREN) ≤40, making it suitable for environments with H2S partial pressures up to 0.3 psi.

Duplex Stainless Steel

Duplex Stainless Steels are two-phase alloys, combining roughly equal amounts of austenite and ferrite. These steels typically contain 20% to 30% chromium, along with molybdenum, nitrogen, and other elements that enhance resistance to pitting and crevice corrosion. As a result, they are ideal for applications in environments with high chloride content. In their annealed state, duplex steels offer yield strengths ranging from 65 to 100 KSI, while cold working can boost the yield strength up to 160 ksi.

Super Duplex Stainless Steels offer improved resistance to elevated temperatures and chloride levels, making them well-suited for demanding conditions such as seawater or water injection wells. Defined by a Pitting Resistance Equivalent Number (PREN) greater than 40, these alloys provide exceptional protection against high chlorides and dissolved oxygen.

Chemical Composition

C
6
Carbon
0.03%
N
7
Nitrogen
0.1%‒0.3%
Si
14
Silicon
0.75%
P
15
Phosphorus
0.03%
S
16
Sulfur
0.03%
Cr
24
Chromium
24%‒26%
Mn
25
Manganese
1%
Fe
26
Iron
59.56%‒67.6%
Ni
28
Nickel
5.5%‒7.5%
Cu
29
Copper
0.2%‒0.8%
Mo
42
Molybdenum
2.5%‒3.5%
W
74
Tungsten
0.1%‒0.5%

Specified Mechanical Properties

API 5CRA / ISO 13680 Group 2 Category 25-7-3
GradeYield
Strength
ksi		Tensile
Strength
ksi		Elongation
%		Hardness
HRC		NACE MR0175/ISO 15156
H2S Sour Service Limits
minmaxminminmax
656590902526Table A.24
(annealed)		H2S ≤ 3.0 psi,
Temp ≤ 450°F
7575100902526
1101101401251136Table A.25
(cold-worked)		H2S ≤ 3.0 psi
1251251501301036
140140160145938140 Grade not recommended for sour service

* Non-standard mechanical properties and grades are made available upon agreement.

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