Internal Pipe Clad (Cladded Pipes)

The Metallurgically bonded (clad) or Mechanically bonded (lined) specification covers seamless and welded clad steel line pipe and lined steel line pipe with enhanced corrosion-resistant properties suitable for use in pipeline transportation systems in the petroleum and natural gas industries. The clad and lined steel line pipe specified herein is composed of a carbon steel backing or base material outside (in some cases inside and/or outside) and a corrosion-resistant alloy (CRA) layer or lining inside of the pipe.

The base material conforms to API 5L (45th Ed.), product specification level (PSL) 2 and applicable annex(es), except as modified herein. Grades of base material covered by this specification include X42, X46, X52, X56, X60, X65, X70, X80, and grades intermediate to these. Grades of the CRA layer are LC 1812, 2205, 2506, 2242, 2262, unified numbering system (UNS) S31703, UNS N08904, UNS N10276, Alloy 31 (UNS N08031), Alloy 59 (UNS N06059), Alloy 254 SMO-11 (UNS S31254), Alloy 400 (UNS N04400), AL6NX (UNS N08367), and EN 1.4529 (UNS N08926). Other grades are subject to agreement between the purchaser and the manufacturer. The delivered product usually has square ends, but other special ends may be furnished by agreement between the purchaser and manufacturer. Included are nominal pipe sizes (NPS) 25 mm (1 in.) through 2134 mm (84 in.). Sizes greater than 2134 mm (84 in.) are outside of the range of API 5L (45th Ed.) but may be supplied up to 2500 mm (100 in.) by agreement, including requirements for materials.

Longitudinal or helical seam CRA clad steel pipe:

Use hot rolling metallurgy composite plate or coil as material, modern advanced pipe-making technology (UOE, JCOE, COE and SAWH) to forming, SAWL or SAWH, and TIG etc. combined automatic welding process to complete welding. The welding quality is stable, and the product size accuracy is high. The composite plate or coil is manufactured by hot rolling technology, which can achieve metallurgical bonding of the atom between corrosion-resistant clad and the backing layer, the binding force reaches above 200MPa, the binding area rate can reach above 99.9%, and the performance is stable and reliable. The clad can meet the corrosion-resistant specific performance requirements, and the backing layer can meet the strength and rigidity condition the structure required.

Seamless or welded Lined steel pipe:

Seamless or welded carbon steel pipe as the outer backing layer, and corrosion-resistant alloy pipe as the inner corrosion layer, using the limit elasticity hydraulic composite method innovated independently by the company achieves the composite between the inner and outer pipe and forms the mechanical liner pipe. Through the composite technology, the optimal composite effect of mechanical liner can be achieved, and the shear stress between inside and outside metal layer can reach 2.0MPa (the relative standard requires 0.2-0.5MPa). Meanwhile, we develops specially the pipe ends automatic overlaying technology and NC machine tools specialized for beveling, which can process complex shape bevels such as U-bevel, and guarantees the conformity of pipe mouth diameter and bevel size, so as to operate pipe jointing on site.

Product materials of CRA clad pipes or lined steel pipes


Q235B, Q345B, Q245R, Q345R, 16MnDR, L245~L485 (API 5L Gr.B, X42~X70), and other backing materials may be used according to user’s requirement.


S30408 (TP304), S30403 (TP304L), S31608 (TP316), S31603 (TP316L), S32168 (TP321), S31803 (LC2205), S31260 (LC2506), N06625 (ASTM B443 625), N08825 (ASTM B424 825), and other corrosion-resistant cladding materials may be used according to user’s requirement.

Pipes made from clad materials meet the highest requirements of durability, corrosion resistance and good value. Their use is recommended in all areas where dynamic stress, high pressure and a high level of corrosives can be found in the media transported. By using clad materials, the excellent strength and toughness of carbon-manganese steels are combined with the corrosion resistance of high-alloyed materials. RELI-CLAD. has been processing clad materials into pipes and piping components for almost 45 years. We process clad pipes into ready-to-install spools.

Ready-to-install clad spools

RELI-CLAD processes clad pipes into spools ready to install. For this we use semi-finished clad material such as welded flanges, elbows, tees and reducers. Prefabrication of clad pipes is used to optimise the pipeline quality and to reduce costs. At an early stage in the production plant, the corrosion resistant layer of the piping components is pickled and passivated and all the non-destructive tests are performed. This leads to considerable potential savings, especially during the subsequent installation of piping systems at the construction site.

Weld overlay cladding is a process that provides protection for metallic components by welding a layer of corrosion-resistant alloy to areas at risk of corrosion and wear. It can be applied to an entire component, or only to specific areas of concern. Typical components clad by RELI-CLAD. include pipes, valves, flanges, connectors, and elbows, as well as more complex geometries such as tee pieces and wye pieces.

Benefits of Cladding


Fully cladding a carbon steel component with alloy 625, as opposed to producing it in solid alloy, can reduce costs by as much as 60%.


  • Only clad the areas at risk. Typical areas include pipe bores, connector seals, ring grooves, valve seats and flange faces.
  • Select appropriate overlay materials for 
your application.


Buy carbon steel components off-the-shelf and clad them in days, rather than waiting 12-16 weeks for specialist forgings.


  • Exotic alloy castings can include sub-surface defects. Cladding the surface produces a very high-quality layer with minimal imperfections.
  • A full range of NDT provides reassurance of quality.

Manufacturing of CRA Clad or Lined Steel Pipes

The CRA clad steel pipe is a bimetallic pipe composed of an internal (and in some cases external) CRA layer that is metallurgically bonded to the backing steel. The cladding may be bonded by hot rolling, coextrusion, weld overlay, explosion bonding, powder metallurgy, or some other process that produces a metallurgical bond. The CRA lined steel pipe consists of a carbon steel or alloy steel pipe with an internal or external CRA liner. The CRA liner is affixed or tightly fitted to the base-metal pipe full length by expansion, compression cold forming, or some other means. The CRA liner may be a tube or pipe inserted into a steel pipe, a plate or sheet rolled into a cylinder by expanding the liner and/ or shrinking the base pipe, or by some other applicable processes. The clad process results in a quite firm metallurgical bonding at the interface of the backing steel and the CRA layer. The mechanical bonding formed by the lining process is relatively “loose” in a lined pipe. Although the clad pipe exhibits better mechanical performance, its cost is relatively higher.

The CRA clad or lined pipes supplied by our company can be sized from 1″ (DN 25) to 100″ (DN 2500) with a minimum CRA layer of 2.5 mm in thickness and a maximum length of 15 meters. Heat treatments for both the base-metal pipe and the CRA layer shall be rigorously conducted. Generally, the line pipe will be furnished in annealed condition while the CRA layer will be furnished in solution-annealed condition. The chemical composition of the backing steel and CRA layer shall be in conformance to its relative material standard specification respectively. Generally, the mechanical properties of the CRA clad or line pipe is determined by the properties of the base material alone. The mechanical propertis of the CRA layer may be specified by the purchaser.

Clad pipes (metallurgically clad pipes)

  • Clad fittings (cold and hot formed elbows, end caps, reducers)
  • Clad induction bends

The components listed above are completed with:

  • Hydroformed clad lined pipes (mechanically clad pipes)
  • Weld overlay pipes
  • Weld overlay fittings (cold and hot formed elbows, end caps, reducers, tees)
  • Weld overlay induction bends

Outer pipes

API 5L grades: X45 – X52 – X60 – X65 – X70

DNV grades: 360MPa – 415MPa – 450MPa – 485MPa

EEMUA grades: EP360 – EP415 – EP450 – EP485

CRA lined pipes

Stainless steels 300 series: S30403, S31603, S31703

Nickel alloys: N04400, N06625 and N08825

Super-austenitic alloys: N08367, S31254, N08904

Pipe Cladding

Protect internal piping from high-pressure corrosive fluids through specialist weld overlay pipe cladding. The process prevents corrosion and damage to pipe systems and avoids potential repair and replacement issues.

Corrosion Resistant Properties

RELI-CLAD weld overlay cladding services are utilised by clients in a vast number of industry sectors where service conditions require corrosion resistant properties. Weld overlay cladding provides the assurance of a heavy-duty metallurgically-bonded protective layer that will not be undermined or dislodged in service. Welding can be overlayered to an application externally (ie flange face) or weld inlay internally (ie through a pipe bore).

Integrity of the cladding can be confirmed in-house via a variety of non-destructive testing (NDT) methods including dye penetrant and ultrasonic.


Typical materials for cladding in common use at Arc Energy include alloy 625, alloy 825, Monel 60, Hastalloy C-22, Hastalloy C-276, Ultimet, Stellite 6 and stainless steels, as well as many less common alloys.

With over 5,000 qualified weld procedures, and the technical expertise to back them up, RELI-CLAD can meet any base material and cladding combination.


RELI-CLAD weld overlay cladding technology utilises a range of processes with great flexibility. An array of component shapes and sizes can be protected, with an equally broad range of base material/cladding alloy alternatives. Whether a one-off special or a large production run is needed, RELI-CLAD ability to clad complex geometries has made weld overlay the most adaptable and flexible anti-corrosion method in use.

Solid CRA, Clad and Lined Pipes


For onshore and offshore pipelines that need to achieve a balance between the mechanical properties of the C-Mn tube steel and the corrosion resistance properties of a Corrosion Resistant Alloy (CRA) RELI-CLAD provides clad and lined pipes.

Production fluids often contain a high sulfur or CO2 content that requires the use of materials suitable for corrosive environments. When the H2S and CO2 content are too high for the corrosion resistance properties of C-Mn steel, a CRA is often employed.

Both clad or lined pipes consist of a C-Mn pipe which has a layer of CRA in contact with the production fluid and hence, its corrosive environment. In the case of clad pipes, the layer of CRA is applied using different procedures that create a metallurgical bond, while in the case of lined pipe an internal CRA pipe is connected to the external C-Mn pipe through mechanical bond.

Cladding Combinations:

Stainless Steels: 304, 304L, 309, 316, 316L, 317L ,321, Duplex SS, Super Duplex SS

Nickel Alloys: Alloy 625, 825, C-22, C-275, C-276 and 6% Molybdenum, Monel 400, 70/30 Copper Nickel

Weld Overlay Clad Pipe Spool Fabrication:

RELI-CLAD Cladding Division has the engineering expertise, experience and knowledge to perform all tasks required for the fabrication of cladded pipe spools.  Our automated butt welding machines ensure a superior quality, faster and more cost-effective process compare with the widely used manual welder method. Our process has a vastly reduced rework percentage with optimum quality being assured with every joint.  RELI-CLAD follows exacting industry standards in all aspects applicable to spool fabrication from initial cutting and beveling right through to hydrotesting, final inspections, creating/packaging and logistics.

A clad pipe combines the strength and toughness of a carbon steel pipe with the corrosion resistance of a stainless or duplex pipe (or even higher grades, as nickel high-alloyed materials like Inconel, Incoloy, etc).

Clad pipes are also called CRA (which stands for “corrosion resistant alloy”).

The cladding process consists of the application, in the inner part of the pipe, of a layer of higher grade material onto a lower-grade base material of the pipe.

Clad pipes are used for fluids that would quickly corrode carbon-manganese steels. The bonding between the two materials is metallurgical and can be achieved by welding the two together or with explosion techniques (whereas lined pipes feature a mechanical bonding of different materials).

Pipe cladding is used to enhance the durability and the resistance to corrosion of a pipe while keeping its final costs at acceptable levels. Of course, clad pipes are more expensive than lined pipes, as the overlay materials used are, generally, noble metals.

Metallurgically clad pipes

Already since the mid eighties we have been producing pipes from metallurgically clad plates for renowned customers all over the world. The tight bond between the metal layers of these pipes is achieved by a diffusion bridge.

Depending on their intended application and technical requirements metallurgically clad pipes are used, for example, as SCR pipes, riser pipes, process or line pipes.

Technical details at a glance:

  • Sizes range OD 114,3 (4″) up to 1 219 mm (48″)
  • Wall thicknesses up to 70 mm
  • Maximum wall thickness / OD ratio 1:10
  • Random lengths up to 24 m (6 m and 12 m lengths without circumferential weld)
  • Suitable for S-Lay and J-Lay method, bundle or reel-lay process

Advantages of metallurgically clad pipes:

  • Reduction of wall thickness
  • Advantages in terms of cost already in case of small dimensions versus full-wall pipes
  • Reduction of weight
  • Wide variety of material combinations possible

Significant cost savings on capital expenditure for production flow lines were achieved by the use of corrosion-resistant alloy (CRA) lined pipe, instead of solid CRA and metallurgically clad pipe options.

Presented here are the materials philosophy of the project team and the rationale for selecting bi-metal-lined pipe along with a description of the manufacture, fabrication, and installation of the flow lines.

Clad pipe

Use of CRA-clad steel line pipe is familiar to the offshore oil and gas industry. In a clad line pipe, the corrosion-resistant alloy forms a complete barrier layer on the internal surface of carbon or low-alloy steel pipe (usually referred to as the “backing steel”). In general, use of clad or bi-metal-lined pipe allows the economic use of expensive CRA materials.

Corrosion resistance to the process environment is provided by the internal CRA clad layer, typically 2.5-3.0 mm thick, while the less expensive carbon backing steel provides the line pipe with the required strength and toughness to maintain the mechanical integrity.

Clad line pipe can be manufactured by various techniques that include the forming and welding of hot roll bonded plate, hot co-extrusion, weld overlay, and manufacture of lined pipe. The details of the various methods of manufacture are well documented.1, 2 For Bruce Phase II development, manufacturing of the CRA-lined pipe was by a process involving hydraulic expansion of a CRA liner pipe inside a carbon-steel outer pipe. The finished product is supplied as bi-metal-lined pipe.

A more-detailed description of the manufacturing process occurs presently.

Manufacture of bi-metal-lined pipe is based upon use of traditional manufacturing routes for the primary materials, carbon-steel outer pipe, and CRA liner pipe.

Tests and Inspection

  • Tensile tests: The CRA layer shall be removed from all specimens of finished products; Longitudinal tensile tests and transverse tensile tests; Weld tensile test (if there is any weld seam in the backing steel).
  • Flattening tests.
  • Guided-bend tests.
  • Fracture toughness tests.
  • Hardness tests (Vikers – ASTM E 384, Rockwell – ASTM E 18).
  • Ferrite/austenite ratio for duplex stainless steel CRA layer.
  • Corrosion tests as per ASTM A262 Practice B or Practice E, ASTM G28 Method A, ASTM G48 Method A.
  • Tests for CRA cladding bond strength and CRA liner tightness.
  • Residual magnetism (less than 15 Gauss).
  • Hydrostatic inspection.
  • Dimensional inspection and visual examination.
  • Ultrasonic inspection for clad pipes.
  • 100% X-Ray inspection for all weld


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