Choosing Pipe Material

Quick pick (TL;DR)

Clean water/steam/hydrocarbons → carbon steel + corrosion allowance.
Chlorides/corrosive → 316/316L (or Duplex if also high-strength).
Sour (H₂S) → NACE-compliant CS or Duplex.
Strong acids → alloy, PFA-lined or GRP.
Buried water/seawater → HDPE or GRP.

Step 1 — Gather the input data

Fluid & corrosive species (Cl, H₂S, acids).
Temperature range & design life.
Corrosion rate & velocity.
P/T for strength; weldability & availability.

Step 2 — Material comparison

Material (spec)	Use for	Limit / watch
CS — A106-B / API 5L	Water, steam, hydrocarbons.	Wet/sour corrosion.
SS 316/316L — A312	Corrosive, chlorides, cryo.	Cl-SCC risk when hot.
Duplex 2205	Seawater, sour, high-strength.	~300°C limit; weld control.
Alloy	Aggressive acids.	High cost.
HDPE	Buried water, drainage.	~60°C; UV/fire.
GRP / FRP	Corrosive chemicals, seawater.	Lower strength.
Lined CS	Strong corrosives, cost-effective.	Liner temp limit.

Step 3 — Corrosion allowance calculation

Worked example — CS line, 20-year life

Given Carbon steel , wet service corrosion rate = 0.10 mm/year design life = 20 years Step 1 — Corrosion allowance CA = rate × life = 0.10 × 20 CA = 2.0 mm Step 2 — Decision add 2.0 mm to the pressure-design thickness if CA > ~3 mm or rate > 0.25 mm/yr → reconsider: upgrade alloy, line, or add inhibitor

Above ~3 mm allowance, upgrading metallurgy is usually cheaper.

Reference — temperature limits

Material	Typical temperature range
HDPE	~ 0 to 60 °C
GRP / FRP	~ −30 to 110 °C
Carbon steel	~ −29 to 425 °C
SS 316 / Duplex	Cryogenic to ~300–550 °C

Failure modes

Mechanism	Avoid by
Cl-SCC	Use Duplex in hot chlorides.
Sour cracking	NACE MR0175 + hardness limits.
Galvanic	Isolate dissimilar metals.
Erosion-corrosion	Limit velocity; harden bends.

Requisition & datasheet

Material/spec, manufacture, size, schedule, CA.
Fittings, flanges, gasket/bolt; lining; NACE.

Frequently asked questions

What should I know about Choosing Pipe Material?

Clean water/steam/hydrocarbons → carbon steel + corrosion allowance. Chlorides/corrosive → 316/316L (or Duplex if also high-strength). Sour (H₂S) → NACE-compliant CS or Duplex. Strong acids → alloy, PFA-lined or GRP. Buried water/seawater → HDPE or GRP.

Which standards or codes apply?

ASME B31.3 App. A (allowable stress); ASTM/ASME A106, A312, A790; API 5L; NACE MR0175 / ISO 15156 (sour).

Standards — ASME B31.3 App. A; A106/A312/A790; API 5L; NACE MR0175.