Valve Material Selection Guide: How to Choose the Right Material for Your Application
Choosing the wrong valve material can lead to corrosion failure, leakage, or catastrophic rupture. The right material depends on four factors: fluid media, temperature, pressure, and corrosion environment. This guide covers every common valve material — from standard carbon steel to exotic alloys — with clear selection criteria for each.
Table of Contents
1. Carbon Steel — The Workhorse Material
Carbon steel is the default valve material for non-corrosive service. It covers approximately 60-70% of all industrial valve applications. Cost-effective, strong, and widely available.
ASTM A216 WCB — Standard Carbon Steel
The most widely used valve body casting material in the world
Use for: Oil & gas (sweet service), water, steam (up to 425°C), air, nitrogen, general hydrocarbons, non-corrosive chemicals. The default material unless corrosion, temperature, or special requirements dictate otherwise.
Avoid for: Seawater, strong acids/alkalis, chloride environments, H2S sour service (unless NACE compliant), temperatures above 425°C or below -29°C.
ASTM A352 LCB / LCC — Low Temperature Carbon Steel
For cryogenic and cold climate service
Use for: Cold climate installations (Arctic, sub-zero), LPG service, refrigeration, ammonia plants, any application where temperature may drop below -29°C. LCB is comparable to WCB but with guaranteed low-temperature toughness.
2. Alloy Steel — High Temperature Service
When temperatures exceed 425°C, carbon steel loses strength due to creep. Chrome-Moly alloy steels maintain strength at elevated temperatures and resist hydrogen attack, making them essential for power plants and refineries.
Chrome-Moly Alloy Steels: WC6, WC9, C5, C12
Essential for high-temperature steam and refinery service
Use for: Main steam lines in power plants, high-temperature refinery service (FCC units, coker units, hydrocracker), hydrogen service (resists hydrogen attack), and any application above 425°C where carbon steel is no longer adequate.
Selection rule: Higher chrome content = higher temperature capability and better hydrogen resistance. WC6 is the most common alloy steel valve material.
3. Stainless Steel — Corrosion Resistance
ASTM A351 CF8M — Austenitic SS316 Equivalent
The standard corrosion-resistant valve material
Use for: Corrosive chemicals (mild acids, alkalis), food & beverage, pharmaceutical, cryogenic service (-196°C with impact testing), offshore topside (non-seawater), and any application where carbon steel corrodes too fast.
Limitation: Susceptible to pitting corrosion in chloride environments (seawater, brines). Not suitable for strong acids (HCl, H2SO4 concentrated), or high-chloride environments. For chloride service, use Duplex or higher alloys.
ASTM A351 CF8 — Austenitic SS304 Equivalent
General purpose stainless steel — no molybdenum
Use for: Mildly corrosive service where CF8M is overkill. Water treatment, food processing, general chemical. Cheaper than CF8M but less corrosion-resistant (no molybdenum).
4. Duplex & Super Duplex Stainless Steel
Duplex stainless steels combine the strength of ferritic steels with the corrosion resistance of austenitic steels. They have a two-phase microstructure (roughly 50% ferrite, 50% austenite) that provides 2x the yield strength of SS316 with superior pitting and stress corrosion cracking resistance.
Duplex 2205 (ASTM A890 CD3MN) vs Super Duplex 2507 (CE3MN)
Duplex 2205 — Use for: Offshore topside process, chloride-containing chemicals, sour service (H2S) with chlorides, desalination, pulp & paper, food processing with aggressive cleaning chemicals.
Super Duplex 2507 — Use for: Seawater (subsea, FPSO, platform), hot chloride brines, aggressive offshore environments, high-pressure seawater injection, and situations where Duplex 2205's PREN is insufficient.
What is PREN?
PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3(%Mo) + 16(%N). Higher PREN = better pitting corrosion resistance. PREN > 40 is generally required for seawater service. Duplex 2205 (PREN ~34) is borderline for seawater. Super Duplex 2507 (PREN ~42) is the standard choice.
5. Exotic Alloys — Severe Service
254 SMO (6% Molybdenum Austenitic)
Use for: Seawater, aggressive chloride environments, bleaching equipment, flue gas desulphurization. Alternative to Super Duplex where an austenitic microstructure is preferred (better weldability, no risk of sigma phase).
Nickel Aluminium Bronze (NAB / C95800)
Use for: Seawater systems (the traditional marine material), fire water, ballast, cooling water in shipboard and offshore platforms. NAB has a unique anti-biofouling property — marine organisms don't attach to it, keeping valves operational without maintenance.
Inconel 625 / Monel 400 / Hastelloy C276
Use for: Inconel — extreme temperature + corrosion (wellhead, subsea). Monel — hydrofluoric acid (HF), seawater, refinery alkylation units. Hastelloy — the "universal" corrosion-resistant alloy for strong acids (HCl, H2SO4, HNO3), wet chlorine gas, and mixed acid environments.
6. Cast Iron & Ductile Iron
Cast Iron (ASTM A126) & Ductile Iron (ASTM A536)
Use for: Water distribution, HVAC, fire protection, low-pressure steam, non-critical general service. Cast iron is the cheapest valve material but is brittle and limited in pressure. Ductile iron (GGG40/GGG50) is stronger and more ductile — preferred for butterfly valves, gate valves, and check valves in water service.
Avoid for: High pressure, shock/vibration service, steam above 230°C, hazardous media. Cast iron is prohibited in oil & gas service by most specifications.
7. Material Selection by Service Condition
| Service Condition | Recommended Material | Notes |
|---|---|---|
| General hydrocarbon (sweet) | WCB | Default choice, -29 to 425°C |
| Sour service (H2S) | WCB/WCC (NACE), Duplex | Max 22 HRC, NACE MR0175 |
| High temperature steam (>425°C) | WC6, WC9, C5 | Chrome-moly for creep resistance |
| Cryogenic (<-29°C) | LCB, LCC, CF8M | Impact tested at design temp |
| Seawater | NAB, Super Duplex, 254 SMO | PREN >40 required |
| Mild corrosion | CF8M (SS316) | Standard corrosion-resistant |
| Chloride environment | Duplex 2205, Super Duplex | Resist pitting and SCC |
| Strong acids (HCl, H2SO4) | Hastelloy C276, Alloy 20 | Universal acid resistance |
| Hydrofluoric acid (HF) | Monel 400 | HF alkylation units |
| Water distribution | CI, DI, WCB | Cost-driven, low pressure |
| Food & pharmaceutical | CF8M (SS316L) | Surface finish Ra ≤ 0.8μm |
| Hydrogen service | WC6, WC9, C5 (Nelson curve) | Chrome resists H2 attack |
| Offshore topside | Duplex 2205, CF8M | Marine atmosphere corrosion |
| Subsea | Super Duplex, Inconel | Extreme corrosion + pressure |
8. Master Material Comparison Table
| Material | ASTM Cast | Temp Range | Corrosion | Strength | Cost | Typical Use |
|---|---|---|---|---|---|---|
| Carbon Steel | A216 WCB | -29 to 425°C | Poor | Good | 1.0x | General oil & gas, water, steam |
| Low Temp CS | A352 LCB | -46 to 340°C | Poor | Good | 1.2x | Cold climate, LPG |
| 1¼Cr-½Mo | A217 WC6 | -29 to 538°C | Poor | High | 1.8x | HT steam, refinery |
| 2¼Cr-1Mo | A217 WC9 | -29 to 593°C | Poor | High | 2.0x | HT steam, H2 service |
| SS316 | A351 CF8M | -196 to 538°C | Good | Medium | 2.5x | Chemicals, cryo, food |
| Duplex 2205 | A890 CD3MN | -46 to 315°C | Very Good | Very High | 3.5x | Offshore, chloride |
| Super Duplex | A890 CE3MN | -46 to 315°C | Excellent | Very High | 5.0x | Seawater, subsea |
| 254 SMO | — | -196 to 400°C | Excellent | Medium | 6.0x | Seawater, FGD |
| NAB | B148 C95800 | -40 to 260°C | Excellent (SW) | Medium | 5.0x | Marine, seawater |
| Inconel 625 | — | -196 to 982°C | Excellent | Very High | 10x | Subsea, wellhead |
| Monel 400 | — | -196 to 480°C | Excellent (HF) | High | 8x | HF acid, seawater |
| Hastelloy C276 | — | -196 to 675°C | Universal | High | 12x | Strong acids, Cl2 |
| Cast Iron | A126 Cl.B | -10 to 230°C | Poor | Low | 0.5x | Water, low-pressure |
| Ductile Iron | A536 | -20 to 350°C | Poor | Medium | 0.6x | Water, HVAC, fire |
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