Selecting the correct disc material is one of the most overlooked — yet most critical — decisions when specifying a butterfly valve. The disc material directly affects corrosion resistance, seat life, torque requirements, and long-term maintenance costs. As a manufacturer serving water treatment, marine, chemical, and industrial customers worldwide, Gaoshan Valves is often asked: aluminum bronze, 316L stainless steel, or 2205 duplex stainless — which is right for my project? This guide breaks down the differences so buyers can specify with confidence.
Why Disc Material Matters
The disc is the only wetted component in constant dynamic contact with the valve seat. A mismatch between disc material and application — whether due to corrosion, galvanic incompatibility, or excessive seat friction — is one of the leading causes of premature butterfly valve failure in the field. Choosing correctly at the specification stage avoids costly downtime later.
Aluminum Bronze (ASTM B148 / UNS C95800)
Aluminum bronze is the traditional standard disc material referenced in AWWA C504 and widely accepted under BS EN 593 / API 609 for rubber-seated butterfly valves used in waterworks applications.
Governing standards: ASTM B148 (Standard Specification for Aluminum-Bronze Sand Castings), UNS C95800, AWWA C504, BS EN 1982
| Property | Value |
|---|---|
| Chemical composition | Cu ≥79%, Al 8.5–9.5%, Ni 4.0–5.5%, Fe 3.5–4.5%, Mn ≤1.5% |
| Tensile strength | ≥620 MPa (90,000 psi) |
| Yield strength (0.5% ext.) | ≥275 MPa (40,000 psi) |
| Elongation | ≥15% |
| Brinell hardness | 150–180 HB |
Strengths:
- Excellent resistance to seawater corrosion and biofouling; approved by major marine classification societies
- Low friction coefficient against EPDM/NBR seats, reducing wear and extending seat life under frequent cycling
- Strong galvanic compatibility with cast/ductile iron valve bodies
Best suited for: municipal water and wastewater systems, seawater intake and desalination plants, marine and port infrastructure, and any project specified to AWWA C504.
316L Stainless Steel (ASTM A351 CF3M / UNS S31603)
316L is the most widely available and broadly applied disc material across general industrial service.
Governing standards: ASTM A351 Grade CF3M (castings), ASTM A276 / A479 (bar), UNS S31603, EN 1.4404 / GB 022Cr17Ni12Mo2
| Property | Value |
|---|---|
| Chemical composition | C ≤0.03%, Cr 17–21%, Ni 9–13%, Mo 2.0–3.0%, Mn ≤1.5% |
| Tensile strength | ≥485 MPa (70,300 psi) |
| Yield strength (0.2% offset) | ≥205 MPa (30,000 psi) |
| Elongation | ≥30% |
| Brinell hardness | ≤183 HB |
Strengths:
- Strong all-around corrosion resistance across a wide range of media, including mild acids and alkalis
- Globally standardized material with consistent mill certification and traceability
- A cost-effective, readily available upgrade path from standard cast iron or bronze discs
Best suited for: chemical processing, food and beverage, general industrial fluid handling, and projects where media composition may vary or is not fully defined at the specification stage.
2205 Duplex Stainless Steel (ASTM A890 Grade 4A / UNS S32205)
2205 duplex combines higher mechanical strength with superior resistance to pitting and chloride-induced stress corrosion cracking.
Governing standards: ASTM A890/A890M Grade 4A (castings), ASTM A182 F51 (wrought), UNS S31803/S32205, EN 1.4462
| Property | Value |
|---|---|
| Chemical composition | Cr 21–23.5%, Ni 4.5–6.5%, Mo 2.5–3.5%, N 0.08–0.20% |
| Tensile strength | ≥620 MPa (90,000 psi) |
| Yield strength (0.2% offset) | ≥450 MPa (65,000 psi) |
| Elongation | ≥25% |
| Brinell hardness | ≤270 HB |
| PREN (pitting resistance) | ≥33 |
Strengths:
- Roughly double the yield strength of standard austenitic stainless steels
- Excellent performance in high-chloride and high-pressure environments
- Extended service life in aggressive chemical or offshore conditions
Best suited for: high-pressure pipelines, offshore platforms, and process lines carrying highly corrosive or high-chloride media.
Quick Selection Guide
| Requirement | Recommended Disc Material |
|---|---|
| AWWA C504 waterworks project | Aluminum Bronze |
| Seawater / desalination / marine | Aluminum Bronze |
| General industrial / chemical service | 316L Stainless Steel |
| Media composition uncertain or variable | 316L Stainless Steel |
| High pressure, high chloride, offshore | 2205 Duplex Stainless Steel |
FAQ
Q: Can 316L be used in place of aluminum bronze for AWWA-spec projects?
A: Yes. AWWA C504 lists stainless steel as an accepted upgrade option to the standard aluminum bronze disc, and many specifications explicitly permit either.
Q: Is 2205 duplex necessary for standard municipal water service?
A: Generally not. 2205 is intended for higher-pressure or highly corrosive conditions; standard municipal water service is well served by aluminum bronze or 316L.
Q: Does Gaoshan Valves supply all three disc material options?
A: Yes. Gaoshan Valves manufactures butterfly valves with aluminum bronze, 316L, and 2205 duplex discs to match project specifications and regional standards. Aluminum bronze discs are produced to order — contact our team for lead time and quotation.
About Gaoshan Valves
Henan Gaoshan Valves Co., Ltd., founded in 1975, is a manufacturer of industrial valves including steam traps, butterfly valves, gate valves, and pressure reducing valves, serving procurement buyers across North America, the Middle East, and beyond.