Direct Answer

Butterfly valves are made from a combination of materials selected for the valve body, disc, stem, and seat. Common body materials include cast iron, ductile iron, carbon steel, stainless steel, and aluminum bronze, while seats are typically made from EPDM, NBR, PTFE, or metal. The best material depends on the fluid, pressure, temperature, and operating environment.

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Why Material Selection Matters

Choosing the right butterfly valve material directly affects:

• Corrosion resistance
• Pressure capability
• Temperature resistance
• Service life
• Sealing performance
• Maintenance costs

A valve used in clean water requires different materials than one handling seawater, steam, chemicals, or abrasive slurries.

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Common Butterfly Valve Body Materials

The valve body provides structural strength and connects the valve to the piping system.

Cast Iron

Cast iron is one of the most economical materials and is commonly used in low-pressure water and HVAC systems.

Advantages

• Low cost
• Good machinability
• Suitable for water applications

Typical applications

• Water distribution
• Irrigation
• HVAC systems

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Ductile Iron

Ductile iron offers higher strength and better impact resistance than cast iron.

Advantages

• Stronger than cast iron
• Good corrosion resistance with coatings
• Cost-effective

Typical applications

• Municipal water
• Wastewater treatment
• Fire protection

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Carbon Steel

Carbon steel is widely used for industrial services involving higher pressures and temperatures.

Advantages

• High mechanical strength
• Excellent pressure resistance
• Good weldability

Typical applications

• Oil and gas
• Power generation
• Petrochemical plants

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Stainless Steel

Stainless steel provides excellent corrosion resistance in aggressive environments.

Common grades include:

• CF8 (304 Stainless Steel)
• CF8M (316 Stainless Steel)
• Duplex Stainless Steel

Typical applications

• Chemical processing
• Food and beverage
• Pharmaceutical plants
• Marine environments

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Aluminum Bronze

Aluminum bronze performs exceptionally well in seawater applications.

Advantages

• Outstanding seawater corrosion resistance
• High strength
• Long service life

Typical applications

• Offshore platforms
• Shipbuilding
• Desalination plants

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Common Disc Materials

The disc is the primary flow-control component and is directly exposed to the process fluid.

Popular disc materials include:

Disc Material	Best For
Ductile Iron (Nickel-Plated)	Water systems
Stainless Steel 304	General industrial service
Stainless Steel 316	Corrosive chemicals
Duplex Stainless Steel	Offshore and seawater
Aluminum Bronze	Marine applications
Hastelloy	Strong acids
Monel	Saltwater and chemical processing

Disc material is often selected independently from the body material to optimize both cost and performance.

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Stem Materials

The stem transfers torque from the actuator to the disc.

Common materials include:

• Stainless Steel 410
• Stainless Steel 420
• Stainless Steel 431
• Stainless Steel 304
• Stainless Steel 316
• Duplex Stainless Steel

These materials provide high strength while resisting corrosion and wear.

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Butterfly Valve Seat Materials

The seat is responsible for sealing when the valve is closed.

EPDM

Best for:

• Water
• Drinking water
• Mild chemicals

Temperature range:

• Approximately -20°C to 120°C

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NBR (Buna-N)

Best for:

• Oil
• Fuel
• Petroleum products

Temperature range:

• Approximately -20°C to 100°C

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PTFE

Best for:

• Corrosive chemicals
• Acids
• Solvents

Temperature range:

• Up to approximately 200°C

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Metal Seat

Metal seats are designed for severe service.

Suitable for:

• Steam
• High temperature
• High pressure
• Abrasive media

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Material Selection by Industry

Different industries require different material combinations.

Industry	Recommended Materials
Water Treatment	Ductile Iron + EPDM
HVAC	Cast Iron + EPDM
Oil & Gas	Carbon Steel + Metal Seat
Chemical Processing	Stainless Steel + PTFE
Marine	Aluminum Bronze or Duplex Stainless Steel
Food & Beverage	Stainless Steel 316 + PTFE
Power Plants	Carbon Steel + Metal Seat

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Factors to Consider When Choosing Materials

Before selecting a butterfly valve, evaluate:

Fluid Type

Water, steam, chemicals, oil, gas, or slurry all require different materials.

Operating Temperature

Higher temperatures may require metal seats or alloy materials.

Operating Pressure

Pressure ratings influence body and seat selection.

Corrosion

Corrosive media often require stainless steel, duplex stainless steel, or special alloys.

Cost

Premium alloys improve durability but increase initial investment.

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Which Material Is Best?

There is no single “best” butterfly valve material.

Instead, the ideal combination depends on the application:

• Water systems: Ductile iron + EPDM
• Chemical plants: Stainless steel + PTFE
• Steam service: Carbon steel + metal seat
• Seawater: Aluminum bronze or duplex stainless steel
• Food processing: Stainless steel 316 + PTFE

Proper material selection maximizes valve life while minimizing maintenance costs.

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Conclusion

Butterfly valves are manufactured using a wide range of materials for the body, disc, stem, and seat to suit different industrial conditions. Cast iron and ductile iron are common for water systems, carbon steel is preferred for high-pressure applications, stainless steel excels in corrosive environments, and specialized alloys such as duplex stainless steel and aluminum bronze are used for offshore and marine service. Selecting the right material combination ensures reliable performance, safety, and long service life.

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Frequently Asked Questions

What is the most common butterfly valve body material?

Ductile iron is one of the most widely used body materials because it offers an excellent balance of strength, durability, and cost for water and wastewater applications.

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Which seat material is best for chemical applications?

PTFE is commonly selected for chemical service because it provides excellent resistance to acids, alkalis, and many corrosive fluids.

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Are stainless steel butterfly valves better than cast iron valves?

Not necessarily. Stainless steel valves provide superior corrosion resistance and are ideal for aggressive media, while cast or ductile iron valves are more economical and well suited to clean water and general industrial services.