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Common Metallic and Non-Metallic Materials for Industrial Valves and Their Corrosion Resistance Characteristics
Created on 08.21
Common Metallic and Non-Metallic Materials for Industrial Valves and Their Corrosion Resistance Characteristics
1. Common Metallic Materials and Their Corrosion Resistance
1.1 Stainless Steels
304 Stainless Steel
- Exhibits good general corrosion resistance against atmospheric exposure, water, weak acids, and weak alkalis.
- Not suitable
for concentrated acids, concentrated alkalis, or strong oxidizing environments.
316 Stainless Steel
- Contains molybdenum (Mo) in addition to the 304 composition, which significantly improves corrosion resistance, particularly against chloride attack.
- Offers better resistance to seawater, chloride solutions, and other aggressive media.
- Widely used in chemical and marine environments where chlorides are present.
Important Note: The "stainless" property of stainless steels is conditional. Under specific conditions such as the presence of chlorides, elevated temperatures, or low pH, pitting or stress corrosion cracking (SCC) may still occur.
1.2 Titanium and Titanium Alloys
- Exhibit excellent corrosion resistance against chlorides, hypochlorous acid, wet chlorine, oxidizing acids, organic acids, and alkalis.
- Not resistant
to hydrofluoric acid, fluorine, fuming sulfuric acid, or caustic alkalis.
- Common grades such as
Ti-0.3Mo-0.8Ni and Ti-0.2Pd offer improved crevice corrosion resistance and are widely used as sealing face materials for vessel and equipment applications.
1.3 Tantalum
- Possesses outstanding corrosion resistance, comparable to glass.
- Resists almost all chemical media except hydrofluoric acid, fuming sulfuric acid, and strong alkalis.
- Due to its high cost, tantalum is generally used only in special anti-corrosion applications.
1.4 Nickel-Based Alloys (Including Hastelloy®)
- Contain high proportions of nickel, chromium, molybdenum, and other elements, providing excellent resistance to both high temperatures and corrosion.
- Withstand many strong acids, strong alkalis, salts, and other aggressive media.
- In chemical instrumentation, these alloys are commonly used for components in direct contact with highly corrosive media.
Common series:
- Hastelloy B-series
- resistant to hydrochloric acid.
- Hastelloy C-series
- resistant to oxidizing acids and mixed acids.
1.5 Aluminium Alloys
The corrosion resistance of aluminium includes both chemical corrosion and stress corrosion resistance. In general:
Series | Alloy Type | Corrosion Resistance (relative ranking) |
1xxx | Pure aluminium | Best |
5xxx | Al-Mg | Good |
3xxx | Al-Mn | Moderate |
6xxx | Al-Mg-Si | Moderate |
2xxx | Al-Cu | Poor |
7xxx | Al‑Zn | Poor |
Selection should be based on the specific service environment and requirements.
2. Common Non‑Metallic Materials and Their Corrosion Resistance
2.1 Plastics
Thermoplastics – e.g. Polytetrafluoroethylene (PTFE)
- Exhibits excellent corrosion resistance, capable of resisting almost all chemical media.
- Widely used for linings, seals, and gaskets.
- Limitation:
Maximum service temperature is generally ≤ 200 °C.
Thermosetting Plastics – e.g. Epoxy Resin
- Offers good corrosion resistance and electrical insulation.
- Used for instrument housings, insulating components, etc.
2.2 Synthetic Rubber
- Provides good elasticity and corrosion resistance.
- Nitrile Butadiene Rubber (NBR)
is suitable for O‑rings and other seals, resisting oil, water, weak acids, and weak alkalis.
- Different rubber grades have different media and temperature resistance ranges; proper matching is essential during selection.
2.3 Ceramics
- Exhibit excellent high-temperature resistance and chemical stability.
- Resistant to most acids, alkalis, and salts.
- Drawbacks:
Brittle and poor impact resistance.
- Commonly used in high-temperature instrument components, but not suitable for high-vibration or impact-prone applications.
3. Key Points for Engineering Material Selection
- "Stainless steel" is not universally resistant:
304 has poor resistance in chloride-containing or reducing acid environments. Although 316 is superior to 304, it may still suffer pitting or stress corrosion cracking in high-temperature, high-concentration chloride service.
- Non-metallic materials ≠ absolute corrosion resistance:
PTFE is nearly universal in chemical resistance, but its temperature and pressure limits must be respected. Rubbers and plastics are subject to ageing; service life should be carefully considered.
- Nickel‑based alloys are not a "panacea":
Although they resist many aggressive media, their high cost demands a trade‑off between performance and economy.
- Balance material cost with corrosion resistance:
Under the premise of meeting process requirements, select the most cost‑effective solution rather than blindly choosing the highest‑grade material.
- Consult corrosion data handbooks:
Before selection, review corrosion data based on the specific medium composition, temperature, concentration, and other service conditions. When necessary, conduct coupon tests for verification.
Appendix: Quick Reference – Corrosion Resistance of Common Materials
Note: The data below are compiled from chemical corrosion handbooks. Final selection should take into account the actual service conditions, including medium purity, temperature, concentration, and flow velocity.
Material | Suitable Media | Unsuitable Media |
304 Stainless Steel | Atmosphere, water, weak acids, weak alkalis | Concentrated acids, concentrated alkalis, strong oxidizers, chloride-containing solutions |
316 Stainless Steel | Seawater, chloride solutions | High-temperature, high-concentration chlorides; strong reducing acids |
Titanium & Titanium Alloys | Chlorides, oxidizing acids, organic acids, wet chlorine | Hydrofluoric acid, fuming sulfuric acid, alkalis |
Tantalum | Almost all chemical media (except HF, fuming H₂SO₄, alkalis) | Hydrofluoric acid, fuming sulfuric acid, alkalis |
Hastelloy® Alloys | Many strong acids, strong alkalis, salts | Depends on specific grade |
PTFE | Almost all chemical media | High temperature (> 200 °C), high pressure |
NBR (Nitrile Rubber) | Oil, water, weak acids, weak alkalis | Strong acids, strong alkalis, high temperatures |
This summary is intended as a practical reference for valve material selection, procurement, and engineering design under corrosive service conditions.
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