Alloy 625 Lined Stainless Steel Pipes

Exceptional Pitting and Crevice Corrosion Resistance:

PRE ≥ 45 (typically 45-50) due to high chromium (20-23%), high molybdenum (8-10%), and niobium (3.15-4.15%) content – the highest among nickel alloys for lined pipe seawater applications.

Ultra-High Strength Lining: 

Yield strength of lining ≥ 415 MPa in annealed condition; cold worked options available.

Outstanding Seawater Compatibility: 

No crevice corrosion or pitting, even in stagnant seawater or high-velocity conditions (up to 20 m/s), significantly outperforming Super Duplex 2507 in long-term seawater exposure.

Superior Chloride SCC Resistance: 

High nickel content (≥58%) provides outstanding resistance to chloride-induced SCC and sulfide-induced SSCC.

Excellent High-Temperature Strength and Oxidation Resistance:

Maintains excellent mechanical properties up to 980°C (1800°F).

Niobium Stabilization – No Sensitization: 

Niobium addition (3.15-4.15%) stabilizes the alloy against intergranular corrosion, eliminating need for post-weld heat treatment.

NACE MR0175 / ISO 15156 Compliant: 

Fully qualified for sour service with highest allowable H₂S partial pressures, documented HIC and SSC test reports available.

Cost-Effective Alternative to Solid Alloy 625: 

Reduces material cost by 70-85% compared to solid Alloy 625 pipe while providing equivalent internal corrosion protection.

Broad Temperature Range: 

Lining suitable from cryogenic (-196°C) to high temperature (980°C).

Weldable End Preparation: 

Available with weld overlay transition (butter layer) using ERNiCrMo-3 (Alloy 625) filler metal.

Full Range of Sizes: 

Available from 2″ to 48″ (DN50 to DN1200) with lining thickness from 2mm to 8mm.

International Certifications: 

Lined pipes can be certified by ABS, BV, DNV, LR, GL, RINA, CCS, KR, and NK, and comply with NORSOK M-650, NACE MR0175, API 17E, API 17D, and ISO 13628-5 standards.

Element

Ni

Cr

Fe

Mo

Nb+Ta

C

Mn

P

S

Si

Al

Ti

Co

Alloy 625

≥58.0

20.0–23.0

≤5.0

8.0–10.0

3.15–4.15

≤0.10

≤0.5

≤0.015

≤0.015

≤0.5

≤0.4

≤0.4

≤1.0

Alloy 625 (UNS N06625) is a nickel-chromium-molybdenum alloy with niobium stabilization. The high molybdenum content (8-10%) and niobium (3.15-4.15%) provide exceptional pitting resistance (PRE ≥ 45), the highest among nickel alloys for seawater lined pipe applications.

Comparison of PRE (Pitting Resistance Equivalent) Values for Lining Materials:

Lining Grade	Nickel (%)	PRE	Seawater Suitability	High-Temperature Capability
316/316L	10-14	24-26	Limited	400°C
Duplex 2205	4.5-6.5	34-35	Good	300°C
Super Duplex 2507	6-8	42-45	Excellent	300°C
Alloy 825	38-46	38-42	Excellent	540°C
Alloy 625	≥58	≥45	Outstanding	980°C

Base Pipe Selection: High-quality carbon steel, high-yield steel, or low-temperature steel base pipe selected based on service pressure, temperature, and depth requirements.
Base Pipe Preparation: Base pipe is cleaned (shot blasting to SA 2.5), inspected for surface defects, and prepared for lining application.
Lining Tube Fabrication: Alloy 625 nickel alloy sheet is rolled and welded into a tube slightly smaller than the base pipe ID using ERNiCrMo-3 (Alloy 625) filler metal.
Lining Insertion: The Alloy 625 lining tube is inserted into the base pipe.
Hydraulic Expansion: High-pressure water (up to 5000 psi) expands the lining tube against the base pipe inner wall, creating a tight mechanical bond.
Solution Annealing: Lining material is in solution annealed condition (1095–1205°C) for optimal corrosion resistance.
Intergranular Corrosion Test: ASTM G28 – mandatory for Alloy 625.
Pitting Corrosion Test: ASTM G48 – upon request.
Weld Overlay (Butter Layer): Pipe ends are prepared with Alloy 625 weld overlay using ERNiCrMo-3 filler metal.
Hydrostatic Testing: Each lined pipe is hydrostatically tested to verify bond integrity and pressure rating.
NDT Inspection: Ultrasonic testing (UT) and eddy current testing (ECT) verify lining thickness and bond quality – 100% coverage.
End Finishing: Pipe ends are beveled per ASME B16.25 and prepared for field welding.
Marking & Coating: Pipes are marked with grade, size, lining thickness, heat number, and standard. External coating (FBE, 3LPE, 3LPP, concrete weight coating) applied upon request.

Parameter	Requirement
Weld Overlay Material	ERNiCrMo-3 (Alloy 625)
Overlay Thickness	3mm – 5mm (minimum)
Overlay Length	50mm – 100mm from pipe end
Overlay Application	GTAW (TIG) or GMAW (MIG) with inert gas shielding
Interpass Temperature	≤150°C
Heat Treatment	Not required (no PWHT necessary)
Preheating	100-150°C for carbon steel base

Base Pipe Inspection: Chemical analysis, mechanical testing, dimensional check, hardness test per API 5L.

Lining Material Verification: PMI 100% for Alloy 625 lining material – verification of Ni (≥58%), Cr (20-23%), Mo (8-10%), Nb (3.15-4.15%).

Intergranular Corrosion Test: ASTM G28 – mandatory for Alloy 625.

Pitting Corrosion Test: ASTM G48 – upon request.

Bond Integrity Testing: Ultrasonic test (UT) to verify bond between lining and base pipe – 100% coverage.

Lining Thickness Check: Ultrasonic thickness measurement at multiple points (minimum 4 points per meter).

Hydrostatic Test: Each pipe tested at 1.5× design pressure – documented.

Hardness Testing: As required for NACE compliance.

Third-Party Inspection: SGS, BV, DNV, TUV, LR, ABS available.

Deepwater Subsea Flowlines: Subsea flowlines, riser systems, pipeline end termination (PLET) jumpers, subsea manifold headers (API 17D compliant, DNV-OS-F101 compliant).

Subsea Umbilical Systems: Umbilical termination assemblies (UTA), chemical injection lines, hydraulic control lines (API 17E, ISO 13628-5 compliant, ABS/BV/DNV certified to 3000m).

Seawater Injection Systems: High-pressure seawater injection flowlines, deepwater seawater lift risers, produced water re-injection lines.

Chemical Injection Skids: Methanol injection lines, MEG injection piping, glycol transfer lines, corrosion inhibitor injection systems.

HP/HT Sour Gas Pipelines: High-pressure, high-temperature sour gas gathering lines, wellhead flowlines (NACE MR0175 compliant, highest H₂S limits).

Offshore Platforms (Critical Chemical Service): Topsides chemical injection piping, produced water treatment lines, HP chemical transfer lines (NORSOK M-650 qualified).

Thermal Oxidizer Interconnecting Piping: High-temperature corrosive gas transfer lines (up to 980°C).

Aerospace Test Stand Piping: High-pressure corrosive fluid transfer lines.

Subsea Chemical Storage and Injection: Chemical storage tank connections, subsea chemical injection point piping.

1. Why choose Alloy 625 lined pipe instead of solid Alloy 625 for subsea umbilical applications?
Alloy 625 lined pipe provides the same internal corrosion resistance as solid Alloy 625 at 15-25% of the material cost for large diameters. The carbon steel base pipe provides structural strength and pressure containment at much lower cost, making it an economical choice for subsea flowlines, umbilical chemical injection lines, and long-distance offshore applications. Cost savings of 75-90% can be achieved, especially for larger diameter pipelines.

2. What is the difference between Alloy 625 and Alloy 825 for lined pipe applications?
Alloy 625 has higher molybdenum (8-10% vs 2.5-3.5%), higher PRE (≥45 vs 38-42), higher strength (YS ≥415 MPa vs ≥240 MPa), and significantly better seawater pitting resistance. For deepwater subsea flowlines, seawater injection lines, and umbilical chemical injection systems, Alloy 625 is preferred. For sulfuric/phosphoric acid service, Alloy 825 is more cost-effective.

3. Can Alloy 625 lined pipes be used for subsea umbilical chemical injection lines?
Yes. Alloy 625 is the industry standard material for subsea umbilical chemical injection lines and hydraulic control lines (API 17E, ISO 13628-5 compliant). Lined pipe construction provides significant cost savings for the carbon steel outer sheath.

4. Are Alloy 625 lined pipes suitable for HP/HT sour service?
Yes. Alloy 625 is fully NACE MR0175 / ISO 15156 compliant for sour service with the highest allowable H₂S partial pressures for nickel-based alloys. HIC and SSC test reports available upon request.

5. What is the maximum service temperature for Alloy 625 lined pipes?
980°C (1800°F) for the lining material in oxidizing atmospheres. However, the carbon steel base pipe limits the overall service temperature to approximately 400-500°C depending on base pipe grade. For high-temperature applications, select appropriate base pipe material (A335 P11/P22).

6. What base pipe material is recommended for deepwater subsea applications?
API 5L X65 or X70 with enhanced collapse resistance (as per DNV-OS-F101) and sour service capability (hardness controlled ≤22 HRC) is recommended for deepwater subsea applications.

7. Can Alloy 625 lined pipes be welded in the field?
Yes, with proper weld overlay (buttering) at pipe ends using ERNiCrMo-3 filler metal. The overlay provides a transition layer allowing welding between carbon steel base pipes while maintaining corrosion resistance. Qualified welding procedures (WPS/PQR) are available.

Outstanding Seawater Resistance: PRE ≥45 – highest among nickel alloys for lined pipe applications

API 17E / ISO 13628-5 Compliant: Suitable for subsea umbilical chemical injection lines

API 17D / DNV-OS-F101 Compliant: Suitable for deepwater subsea flowlines

NACE MR0175 / ISO 15156 Compliant: Highest H₂S partial pressure tolerance for sour service

NORSOK M-650 Qualified: Complete offshore documentation packages

ASTM G28 Intergranular Tested: Mandatory corrosion resistance verification

Cost-Effective: 75-90% cost savings compared to solid Alloy 625 pipe

Full Traceability: Heat number on each pipe – traceable to original mill certificate

Complete Size Range: 2″ to 48″ (DN50 to DN1200) – standard and custom sizes

Multiple Base Pipe Grades: API 5L X52-X70, A106 Gr B, A333 Gr 6, A694 F52-F65

Lining Thickness Options: 2mm to 8mm – tailored to your service severity

Weld Overlay Ready: Pipe ends prepared with ERNiCrMo-3 butter layer for field welding

Third-Party Inspection: SGS, BV, DNV, TUV, LR, ABS available

Global Delivery: Exported to major deepwater subsea, umbilical, and extreme service projects worldwide (Gulf of Mexico, North Sea, Brazil Santos Basin, West Africa, SE Asia)

Website: www.womicstainless.com

E-mail: info@womicstainless.com

Tel / WhatsApp / WeChat:

Victor: +86 15575100681

Jack: +86 18390957568

Womic Steel – Your reliable partner for high‑quality stainless steel products, precision machined components, and custom solutions for corrosion‑resistant applications.

Stock Examples (Alloy 625 Lined Pipes – API 5L X65 Base – 3mm Lining – Weld Overlay Ends – Deepwater Subsea):

NPS	DN	Base Pipe Schedule	Lining Thickness	Base Pipe Grade	Typical Application	Water Depth
4″	100	Sch 80	3mm	API 5L X65	Subsea chemical injection	3000m
6″	150	Sch 80	3mm	API 5L X65	Subsea umbilical lines	3000m
8″	200	Sch 60	4mm	API 5L X65	Subsea flowlines	2500m
10″	250	Sch 60	4mm	API 5L X65	Seawater injection	2000m
12″	300	Sch 40	5mm	API 5L X70	Deepwater riser systems	3000m
16″	400	Sch 40	5mm	API 5L X70	PLET jumper flowlines	2500m
20″	500	Sch 30	6mm	API 5L X70	Deepwater trunk lines	2000m
24″	600	Sch 30	6mm	API 5L X70	Offshore export pipelines	1500m

Stock Examples (Alloy 625 Lined Pipes – API 5L X65 Base – 4mm Lining – NACE MR0175 – HP/HT Sour Gas):

NPS	DN	Base Pipe Schedule	Lining Thickness	Base Pipe Grade	Typical Application	H₂S Service
4″	100	Sch 80	4mm	API 5L X65	HP/HT sour gas gathering	Yes
6″	150	Sch 80	4mm	API 5L X65	Wellhead flowlines	Yes
8″	200	Sch 60	5mm	API 5L X65	HP gas export headers	Yes
10″	250	Sch 60	5mm	API 5L X70	Sour gas pipelines	Yes

Stock Examples (Alloy 625 Lined Pipes – Subsea Umbilical Chemical Injection – API 17E Compliant):

NPS	DN	Base Pipe Schedule	Lining Thickness	Base Pipe Grade	Typical Application	Standard
2″	50	Sch 80	2.5mm	API 5L X52	MEG injection lines	API 17E
3″	80	Sch 80	3mm	API 5L X52	Methanol injection	API 17E
4″	100	Sch 80	3mm	API 5L X52	Chemical injection main	API 17E

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