Super 13Cr tubing occupies a specific and important position in the CRA (corrosion resistant alloy) selection framework for oil and gas wells: it is the step up from L80 13Cr when CO₂ partial pressure, temperature, or chloride concentration exceed what standard 13Cr can handle, without requiring the significant cost and procurement complexity of duplex stainless steel or nickel alloys. For gas condensate wells with high CO₂ and moderate temperatures, Super 13Cr is frequently the most cost-effective CRA solution — providing meaningfully better corrosion resistance than L80 13Cr at a fraction of the cost of higher CRA grades.
ZC Steel Pipe supplies Super 13Cr tubing and casing to project-specific material requirements, with full corrosion qualification data, EN 10204 3.2 MTC, and third-party inspection. We supply CRA tubulars to operators and EPC contractors working in CO₂-corrosive gas and gas condensate fields across Africa, South America, and Southeast Asia. This guide covers Super 13Cr specifications, its corrosion resistance envelope, comparison against L80 13Cr, H2S limitations, and purchase order guidance.
What Is Super 13Cr?
Super 13Cr — also called modified 13Cr, 13Cr-110, or Super 13Cr-110 depending on the mill — is a martensitic stainless steel tubular grade that builds on the 13% chromium base of L80 13Cr with significant additions of nickel and molybdenum. These alloying additions do two things simultaneously: they extend the corrosion resistance envelope to higher temperatures and chloride concentrations, and they raise the achievable yield strength from L80 13Cr's 80 ksi ceiling to 110 ksi or higher.
Super 13Cr is not a defined API 5CT grade. Each mill produces it to a proprietary specification — Vallourec's VM 13Cr-110, Tenaris's 13Cr-110, and similar designations from other producers all fall under the "Super 13Cr" category but may have different exact chemistries and qualified corrosion envelopes. This makes mill selection and corrosion qualification data more important for Super 13Cr than for standard API grades.
Typical Chemical Composition
| Element | L80 13Cr (API 5CT) | Super 13Cr (typical) |
|---|---|---|
| Chromium (Cr) | 12.0–14.0% | 12.0–14.0% |
| Nickel (Ni) | ≤ 0.50% | 4.0–6.0% |
| Molybdenum (Mo) | ≤ 0.50% | 1.0–2.0% |
| Carbon (C) | ≤ 0.22% | ≤ 0.03% |
| Manganese (Mn) | ≤ 1.00% | ≤ 1.00% |
| Silicon (Si) | ≤ 1.00% | ≤ 0.50% |
The key chemistry differences — higher Ni and Mo, much lower C — are responsible for Super 13Cr's improved performance:
Nickel (4–6%) stabilises the austenite phase during heat treatment and improves toughness and corrosion resistance in chloride-containing environments. It also allows the very low carbon content without sacrificing hardenability.
Molybdenum (1–2%) significantly improves resistance to pitting and crevice corrosion in chloride environments, and extends the temperature range over which the passive chromium oxide film remains stable.
Very low carbon (≤ 0.03%) prevents chromium carbide precipitation at grain boundaries during welding and heat treatment — a critical improvement over L80 13Cr (≤ 0.22% C) that makes Super 13Cr far more resistant to sensitisation-induced intergranular corrosion.
Mechanical Properties
| Property | L80 13Cr | Super 13Cr-95 | Super 13Cr-110 | Super 13Cr-125 |
|---|---|---|---|---|
| Min yield strength | 552 MPa (80 ksi) | 655 MPa (95 ksi) | 758 MPa (110 ksi) | 862 MPa (125 ksi) |
| Max yield strength | 655 MPa (95 ksi) | 758 MPa (110 ksi) | 965 MPa (140 ksi) | 1034 MPa (150 ksi) |
| Min tensile strength | 655 MPa (95 ksi) | 724 MPa (105 ksi) | 862 MPa (125 ksi) | 931 MPa (135 ksi) |
| Heat treatment | Q+T | Q+T | Q+T | Q+T |
| Hardness limit | 23 HRC | Mill-specific | Mill-specific | Mill-specific |
Super 13Cr-110 is by far the most common designation, providing 110 ksi yield strength that matches P110 while delivering significantly better CO₂ corrosion resistance. The 95 ksi variant is used when L80 13Cr lacks sufficient pressure containment but full 110 ksi yield is not required.
Corrosion Resistance Envelope
Super 13Cr's corrosion resistance advantage over L80 13Cr is real but bounded. Understanding those bounds is critical to correct material selection.
CO₂ partial pressure: Super 13Cr is effective at CO₂ partial pressures up to approximately 10 bar, depending on temperature and chloride content. At lower temperatures and lower chloride concentrations, the tolerable CO₂ partial pressure is higher.
Temperature: Super 13Cr extends the upper temperature limit from L80 13Cr's approximately 150°C to 175–200°C, depending on CO₂ partial pressure and chloride concentration. Above 200°C, localised pitting risk increases significantly.
Chloride concentration: Super 13Cr tolerates higher chloride concentrations than L80 13Cr, particularly at elevated temperature. The Ni and Mo additions stabilise the passive film against chloride attack.
pH: Both 13Cr grades perform poorly at very low pH (below approximately 3.5). In-situ pH in the wellbore, calculated from CO₂ partial pressure and water chemistry, should always be confirmed against the mill's qualified envelope.
Super 13Cr Corrosion Envelope vs L80 13Cr
| Condition | L80 13Cr | Super 13Cr-110 |
|---|---|---|
| Max operating temperature | ~150°C | ~175–200°C |
| CO₂ partial pressure limit | ~3–5 bar | ~7–10 bar |
| Chloride tolerance | Moderate | Good |
| H2S tolerance | Very low | Very low — slightly better |
| pH minimum | ~3.5 | ~3.5 |
| Elemental sulphur | Not suitable | Not suitable |
| Strong acids | Not suitable | Not suitable |
H2S Limitations
This is the most important constraint on Super 13Cr selection. Martensitic stainless steels — including both L80 13Cr and Super 13Cr — are susceptible to sulphide stress cracking in H2S environments. Super 13Cr's higher yield strength (110 ksi) makes it more susceptible to SSC than L80 13Cr (80 ksi).
NACE MR0175 / ISO 15156-3 permits martensitic stainless steels in H2S service only within specific environmental limits — typically very low H2S partial pressure (often below 0.003 bar) combined with temperature and pH conditions that fall within the qualified envelope for the specific alloy and heat treatment.
For wells with meaningful H2S alongside CO₂:
| Condition | Recommended material |
|---|---|
| CO₂ dominant, H2S < 0.003 bar | Super 13Cr — verify mill envelope |
| CO₂ + moderate H2S | Duplex stainless steel (22Cr or 25Cr) |
| High H2S + high pressure + high temperature | 25Cr duplex or nickel alloys |
Do not specify Super 13Cr for wells where H2S partial pressure exceeds the mill's qualified limit. SSC failure in a production tubing string is a well integrity event with significant safety and commercial consequences.
Connection Types for Super 13Cr
Standard API connections — STC, LTC, BTC — are not appropriate for Super 13Cr tubing in most applications. The reasons are both mechanical and corrosion-related:
Mechanical: Super 13Cr at 110 ksi yield requires a connection rated to full body yield for deep wells. BTC's tensile efficiency is inadequate for 110 ksi strings at typical gas well depths.
Corrosion: The thread compound used in API connections can trap corrosive fluids at the thread interface. Premium metal-to-metal seal connections eliminate this risk and provide gas-tight integrity required for gas condensate production.
Premium connections are the standard specification for Super 13Cr tubing in all but the shallowest, lowest-pressure applications. ZC Steel Pipe supplies Super 13Cr with premium connections qualified for CRA service.
Standard Sizes
| OD (inches) | OD (mm) | Common Weights (lb/ft) | Typical Application |
|---|---|---|---|
| 2⅜ | 60.3 | 4.00–6.40 | Tubing — small-bore gas condensate wells |
| 2⅞ | 73.0 | 6.40–10.40 | Tubing — most common Super 13Cr size |
| 3½ | 88.9 | 7.70–12.95 | Tubing — high-rate gas condensate |
| 4 | 101.6 | 9.50–14.00 | Tubing — large-bore production |
| 4½ | 114.3 | 9.50–15.10 | Tubing / small production casing |
| 5 | 127.0 | 11.50–18.00 | Production casing |
| 7 | 177.8 | 17.00–29.00 | Intermediate casing (less common) |
How to Specify Super 13Cr on a Purchase Order
- Grade designation — Super 13Cr, 13Cr-110, or mill-specific designation
- Minimum yield strength — 110 ksi (758 MPa) standard; specify 95 or 125 ksi if required
- OD and nominal weight
- Connection type — premium connection designation (mandatory for most applications)
- Range — typically R2 for tubing
- Corrosion qualification data required — temperature, CO₂ partial pressure, chloride concentration, pH for the specific well
- H2S partial pressure — confirm within mill's NACE MR0175 qualified envelope
- Charpy impact testing — temperature per project specification
- Quantity — in joints or metric tonnes
- MTC level — EN 10204 3.2 (third-party witnessed)
- Third-party inspection scope — mill visit, witness mechanical and corrosion testing
References
- ISO 15156 / NACE MR0175 — Materials for Use in H2S-Containing Environments
- ISO 13680 — Petroleum and Natural Gas Industries: CRA Seamless Tubes for Use as Casing, Tubing and Coupling Stock
- EFC Publication 16 — Guidelines on Materials Requirements for Carbon and Low Alloy Steels for H2S-Containing Environments in Oil and Gas Production