SUS321 stainless steel VS. SUS430: Corrosion resistance
Apr 16, 2025
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SUS321 vs. SUS430 Stainless Steel Corrosion Resistance: How to Choose the Right Material?
When selecting stainless steel materials, corrosion resistance is one of the top priorities for engineers and procurement professionals. SUS321 and SUS430 are two widely used stainless steel grades, representing austenitic and ferritic types respectively. They differ significantly in their corrosion behavior and are suitable for different application environments.
Surface treatment of SUS321 stainless steel plate
1. SUS321 vs. SUS430 Stainless Steel：Basic Composition and Structure Comparison
| Property | SUS321 (Austenitic) | SUS430 (Ferritic) |
|---|---|---|
| Main alloying elements | Cr, Ni, Ti | Cr |
| Nickel content | 9%–12% | None (or very low) |
| Titanium content | Yes (stabilizes austenite, prevents intergranular corrosion) | No |
| Microstructure | Austenitic | Ferritic |
2. SUS321 vs. SUS430 Stainless Steel：Corrosion Resistance Performance Comparison
| Environment | SUS321 corrosion resistance | SUS430 pitting |
|---|---|---|
| Atmospheric corrosion | Excellent (including marine environments) | Good (suitable for dry indoor or inland environments) |
| Chloride-rich environments (e.g., salty air or water) | Strong resistance, moderate pitting resistance | Prone to pitting and stress corrosion cracking |
| Acidic environments (e.g., sulfuric, phosphoric acids) | Good tolerance in low-concentration acids | Poor acid resistance, not recommended |
| Intergranular corrosion | Low risk (Ti stabilizes carbides at grain boundaries) | Higher risk; requires careful thermal/weld control |
| High-temperature oxidation | Suitable for long-term exposure up to ~870°C | Less stable; oxide layers may peel under heat |
3. SUS321 vs. SUS430 Stainless Steel：Application Recommendations
When to choose SUS321:
Environments requiring moderate to high corrosion resistance, such as petrochemical equipment, heat exchangers, aerospace components.
Exposure to intermediate or high temperatures (600–870°C).
Welded structures that must maintain corrosion resistance over time.
When to choose SUS430:
Cost-sensitive projects in low-corrosion settings, such as kitchen appliances, decorative panels, indoor trim.
Environments that do not involve acids or chloride exposure.
Applications that require magnetic properties (SUS430 is magnetic).
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