Clad Pipe, Tube & Fittings
The same composite principle, formed into a tube: a corrosion-resistant alloy surface on a pressure-bearing carbon steel wall, fused atom to atom. Round clad pipe, clad square and rectangular tube, and mechanical lined pipe — the inside behaves like an all-alloy pipe alloy, the structure is priced like carbon steel.
From plate to pipe,
without losing the bond.
Clad pipe starts from the same composite billet as our clad plate, then is formed and welded into a tube. Two metals are doing two clearly separate jobs.
Three tube products,
one corrosion-resistant surface.
All three put alloy on the side the process fluid touches. What differs is how that alloy is joined to the base pipe — and that is what decides the pressure it can take, the service it suits and the price per metre. Clad pipe and clad square and rectangular tube are metallurgically bonded; lined pipe is not. Square tube and rectangle tube are both made to order — tell us the section and the wall thickness, not just the steel grade.
| Form | seamless or welded |
| Outer diameter | 25 – 2,134 mm |
| Wall thickness / liner | 6 – 70 mm / 1 – 3 mm |
| Bond | metallurgical, ≥210 MPa |
| Standards | API 5LD, GB/T 31940, SY/T 6623 |
| Square tube (SHS) | 20 × 20 – 400 × 400 mm |
| Rectangle tube (RHS) | 20 × 40 – 300 × 500 mm |
| Wall thickness | 1.5 – 16 mm |
| Stainless surface | 0.5 – 3 mm, one side or all |
| Standards | GB/T 6728, EN 10219, ASTM A554 |
| Other sections | custom sizes on request |
| Form | welded base pipe, expanded liner |
| Outer diameter | 60 – 1,220 mm |
| Liner | 2 – 3 mm |
| Pressure design | outer pipe only |
| Typical application | medium / low pressure |
Not sure which one your line needs? Send the medium, chloride level, pressure and temperature and we will say so plainly — including when the cheaper option is enough. Round clad pipe, clad square and rectangular tube, and lined pipe can be consolidated into one shipment.
Metallurgical or mechanically bonded?
Both products are sold as “clad pipe” in the market, but they are not interchangeable. If your line runs at high pressure, carries sour gas (H₂S) service, or will be bent and buried, the difference decides whether the liner is still in place in ten years.
| Metallurgically bonded | Mechanically bonded (lined) | |
|---|---|---|
| How it is made | Composite billet, hot rolled, then formed and welded — or explosive welding of a liner | Liner tube inserted and expanded hydraulically until it grips the base pipe |
| Interface | Atom-to-atom fusion across the full contact area | Friction and interference fit only |
| Bond / shear strength | ≥210 MPa shear, against the 137.8 MPa floor of API 5LD | Friction only — no metallurgical shear value |
| Liner thickness | 1–3 mm, selected to suit the service conditions | 2–3 mm, limited by the expansion process |
| Counted in pressure design | Yes — the composite pipe wall carries load as one | No — only the outer pipe is designed for pressure |
| Behaviour when bent | Bends and forms with the pipe, no separation | Risk of liner wrinkling, buckling and gap formation |
| Behaviour under thermal cycling | Stable — expansion is matched across the bond | Differential expansion can open the interface |
| Typical service | High pressure, sour gas (H₂S) service, offshore, subsea, deep wells | Medium and low pressure, onshore gathering and water lines |
| Relative cost | Higher | Lower |
We manufacture and supply both. If a mechanical liner is genuinely sufficient for your service we will say so — there is no reason to pay for a metallurgical bond you will never stress.
The corrosion performance of alloy,
at a fraction of the alloy cost.
An all-alloy line is the simple answer, and for short runs of small diameter it is often the right one. Beyond a certain size and length, clad pipe wins on every measure that matters to a project.
Where clad pipe is in service today
Six operating conditions, six liner choices — the pipe itself is the same product every time. Which liner you get is decided by the medium, never by the production method.
| Application | Why it is hard | Recommended liner |
|---|---|---|
| Oil & gas gathering | Wet CO₂ and H₂S gathering lines, flowlines and trunk lines — carbon steel corrodes from the inside out. | 316L / 2205 / 625 + X65 |
| Subsea & deepwater | Flowlines, risers and water-injection lines: chloride stress corrosion cracking, 25-year design life, low temperature. | 2507 / 625 / C-276 + X65 |
| Petrochemical & refining | Overhead transfer lines, sour-water, amine and caustic circuits — chlorides and organic acids, long pipe runs. | 316L / 825 / C-276 |
| Desalination | High-pressure brine piping and reverse-osmosis seawater headers — chloride-rich seawater at high flow. | 2205 / 2507 |
| Power & FGD | Absorber recirculation lines, limestone slurry and gypsum dewatering pipework — low pH, corrosion plus abrasion. | 316L / 2205 / C-276 |
| Mining & tailings | Slurry and tailings transport where abrasion and corrosion arrive together. | Cr26 / 316L + Q235B |
304 / 316L — general corrosion, food, water and dilute acids. · 2205 duplex — chlorides, seawater and brine. · 825 / 625 / C-276 — sour gas (H₂S) service, high temperature and aggressive acids. If you are unsure, send us the medium, the chloride level and the operating temperature and we will specify it for you.
The whole line in one material
A clad line is only as good as its weakest component. We supply matching clad pipe fittings made from the same composite, so the alloy bore runs unbroken from end to end and there is no carbon steel exposed to the medium at a joint.
Handled like the carbon steel line
you already build
Six fabrication steps, all of them ordinary line-pipe practice. Only the root weld pass changes.
| Operation | What is done | What to watch |
|---|---|---|
| Bevel preparation | Machined from the carbon-steel side with a small land on the liner, so the welder can see where the two metals meet. | The root weld pass must be made in alloy. |
| Root weld pass | A corrosion-resistant root weld pass with alloy or nickel-base filler matched to the liner; backing gas purges the bore. | Closes alloy-to-alloy. |
| Fill & cap | The rest of the joint is filled and capped with carbon steel filler using normal procedures. | Each weld pass follows the WPS. |
| Bending | Cold bending, induction bending and heat treatment are all acceptable. | Keep the liner on the compression side. |
| Inspection | Radiography or UT of girth welds, plus PMI on the root weld pass; hydrostatic test to your line class. | Protection must not stop at the pipe. |
| Field installation | Laying, lowering in, backfilling and tie-in use ordinary line-pipe equipment. | Only the root weld pass differs. |
In a clad line the fittings are the weak point: one carbon steel elbow is where corrosion starts, and the whole line eventually has to come out. We supply pipe, bends and fittings from the same composite, so the barrier runs unbroken from wellhead to storage.
Dimensions and standards
| Standard | Covers |
|---|---|
| API 5LD | CRA-clad or lined steel pipe — the key international specification; shear strength floor 137.8 MPa |
| GB/T 31940 | Bimetal composite pipe for fluid service — Chinese national standard |
| SY/T 6623 | CRA composite pipe for oil and gas gathering and transmission |
| ASTM A928 | Ferritic/austenitic stainless steel pipe with added filler metal, electric fusion welded |
| ASTM A790 / A789 | Duplex and super duplex stainless steel pipe |
| DNV-OS-F101 | Submarine pipeline systems — offshore and subsea projects |
| GB/T 6728 · EN 10219 | Cold-formed square and rectangular hollow sections — dimensional and tolerance basis for clad square and rectangular tube |
| NACE MR0175 / ISO 15156 | Materials for sour gas (H₂S) service; hardness limits and heat treatment |
Dimensional ranges shown are the envelope we manufacture to. Confirm the exact combination with us before finalising your line class, and we will issue a material test certificate against the standard your project calls for.
Send us the line class
and we will size the pipe.
Process medium, chloride level, operating pressure, temperature and length — that is enough for us to specify the liner and come back with a price. Isometrics and material take-offs welcome.