Pipe materials are chosen to contain a process fluid safely for the design life at the design pressure and temperature, while resisting corrosion, erosion and brittle fracture at the lowest cost. In process plants the main families are carbon steel, low-alloy (chrome-moly) steel, stainless steel, non-ferrous alloys and non-metallic materials. This page is the starting point for the Aienginear pipe material guides.
Pipe material families at a glance
| Family | Common specifications | Typical use | Guide |
|---|---|---|---|
| Carbon steel | ASTM A106 Gr B, API 5L, ASTM A53, ASTM A333 Gr 6 (low temperature) | Hydrocarbons, steam, water and utilities in non-corrosive service; the default choice in most plants | Carbon steel piping materials |
| Low-alloy (Cr-Mo) steel | ASTM A335 P11, P22, P5, P9, P91 | High-temperature steam and hydrogen service where creep and high-temperature hydrogen attack matter | Alloy steel in piping |
| Stainless steel | ASTM A312 TP304/304L, TP316/316L, TP321, TP347; duplex A790 | Corrosive, cryogenic, high-purity and high-temperature service | Types of stainless steel in process piping |
| Non-ferrous alloys | Copper, copper-nickel, nickel alloys (Monel, Inconel, Hastelloy), titanium, aluminium | Seawater, strong acids and chlorides, oxygen and specialised chemical service | Non-ferrous materials for process piping |
| Non-metallic | GRP/GRE, HDPE, PVC/CPVC, PP, PVDF, PTFE-lined steel | Cooling water, firewater, chemicals, drainage and buried service | Non-metallic piping materials |
How to select a pipe material
- Design pressure and temperature – set the allowable stress and wall thickness under ASME B31.3 and rule out materials outside their temperature limits.
- Fluid corrosivity – corrosion rate, chlorides, H₂S (sour service to NACE MR0175/ISO 15156), CO₂, oxygen and erosion.
- Low-temperature toughness – impact-tested grades such as A333 Gr 6 or austenitic stainless steel below the minimum design metal temperature.
- Fabrication and weldability – preheat, PWHT and qualified procedures add cost to alloy materials.
- Life-cycle cost – a corrosion allowance on carbon steel against a corrosion-resistant alloy with no allowance.
For a step-by-step method with worked comparisons, read the pipe material types and selection guide. Related references: pipe sizes and schedules, what is a pipe and pipe class, piping specifications and components and the piping materials interview questions.
Written by Muhammad Raza
Founder of Aienginear. Mechanical engineer (BSc, UET Lahore) and Head of Projects with 18+ years managing piping, mechanical installation, plant shutdowns and turnarounds in power, cement, fertilizer and oil & gas plants.
