Home > Welded Tubes > ASTM A789 / ASTM A790
Built for extreme environments: high pressure, high chloride, high corrosion.
Duplex (22% Cr) and Super Duplex (25% Cr) stainless steels are the workhorses of modern offshore, subsea, desalination, chemical and power industries.
These materials combine the best of two worlds:
Result:
For engineering teams designing pipelines, risers, manifolds and corrosion-critical components, ASTM A789 / A790 duplex tubes offer unmatched dependability.
These are welded stainless-steel tubes manufactured from duplex alloys that contain a balanced austenite–ferrite microstructure.
They provide:
These materials outperform 316 / 317 stainless steel in nearly all severe environments.
Duplex alloys deliver 2× the yield strength of 316, enabling:
| Alloy | PREN |
| 316L | ~25 |
| Duplex 2205 | ~35 |
| Super Duplex 2507 | >40–45 |
Higher PREN = higher pitting & crevice corrosion resistance.
Although duplex and super duplex alloys cost more upfront, their lifespan and performance drastically reduce maintenance cost.
| Standard | Covers | Use Case |
| ASTM A789 | Seamless & welded duplex tubes | Heat exchangers, condensers, instrumentation |
| ASTM A790 | Seamless & welded duplex pipe | Process piping, offshore risers, manifolds |
Both standards cover Duplex & Super Duplex materials but differ in dimensional & mechanical requirements.
Applications include subsea manifolds, offshore platform piping, umbilicals, chemical injection lines, firewater systems, RO brine lines, condensers, and seawater cooling systems.
| OD (mm) | WT (mm) | Typical Applications |
| 6 – 19.05 | 0.8 – 2.0 | Instrumentation & chemical injection |
| 19.05 – 38.1 | 1.0 – 3.0 | Heat exchangers |
| 38.1 – 60.3 | 2.0 – 5.0 | Process piping |
| 60.3 – 114.3 | 3.0 – 8.0 | Offshore manifolds |
| 114.3 – 168.3 | 4.0 – 10.0 | High-pressure brine lines |
Lengths: Standard 6m / 12m · Custom cut-to-length as per project isometric.
Duplex offers ~2× strength and far superior chloride SCC resistance, reducing wall thickness and lifecycle cost. For very high chloride, high-pressure, subsea, or desalination environments where PREN >40 is required. Yes—when welded with controlled heat input and tested. INOX supplies project-approved welded tubes with NDT. Yes—DNV, BV, LR, TUV inspections available. Why choose duplex over 316L?
When should Super Duplex 2507 be used?
Are welded duplex tubes reliable for offshore use?
Do you supply third-party inspected material?