Understanding the corrosion resistance of stainless steel 1.4301 (304) and 1.4401 (316)， is to accurately select materials in different corrosive environments such as chemical, marine, and food. The former is cost-effective in conventional neutral media but has limited chloride ion resistance. The latter contains 2-3% molybdenum, which significantly improves salt spray, acid and alkali, and crevice corrosion resistance, thereby avoiding material failure caused by medium characteristics (such as Cl⁻ concentration, acidity and alkalinity), ensuring long-term safe operation of equipment and controlling costs.
We offer 1.4301 and 1.4401 stainless steel pipes. For detailed specifications and product information, please visit the following website.
Let's analyze the following points：
| Property | 1.4301 (AISI 304) | 1.4401 (AISI 316) |
|---|---|---|
| Chromium (Cr) | 17.5–19.5% | 16.5–18.5% |
| Nickel (Ni) | 8.0–10.5% | 10–13% |
| Molybdenum (Mo) | None | 2.0–2.5% (critical for corrosion resistance) |
| Carbon (C) | ≤0.07% | ≤0.07% |
| Pitting Resistance Equivalent (PREN) | 19–21 (moderate pitting resistance) | 26–30 (significantly improved pitting resistance) |
| Test Method | 1.4301 | 1.4401 |
|---|---|---|
| Salt Spray Test (ASTM B117) | 500–1000 hours (white rust) | 2000–3000 hours (no visible rust) |
| Pitting Potential (ASTM G61) | ~+200 mV (vs SCE) | ~+500 mV (vs SCE) |
| Intergranular Corrosion Risk | Requires solution annealing after welding | Reduced risk with low-carbon variant (1.4404) |
| Sulfuric Acid Resistance (5% H₂SO₄, 25°C) | Corrosion rate: 0.1 mm/year | Corrosion rate: 0.01 mm/year |
2.1 Chloride-containing environments (e.g. seawater, saline solutions)
1.4301 stainless steel Chloride ion resistance: Good performance in environments with low chloride concentrations (e.g. fresh water, food contact), but prone to pitting and crevice corrosion in environments with high chloride ions (e.g. seawater, swimming pool water).
Salt spray test (ASTM B117) Life: Visible corrosion will only occur after about 1000 hours in 5% NaCl solution.
1.4401 stainless steel Chloride ion resistance: Excellent chloride ion resistance due to molybdenum. Ideal for marine applications, chemical processing and offshore equipment.
Pitting potential (ASTM G48) is about 300-500 mV higher than 1.4301, indicating that its passive film is more stable and can effectively resist chloride ion attack.
2.2 Acid and Alkali Environment
1.4301 Stainless Steel Acid Resistance: Oxidizing Acid (e.g. nitric acid): Excellent corrosion resistance; used for nitric acid storage, Non-oxidizing Acid (e.g. sulfuric acid, hydrochloric acid): Only resistant to dilute solutions; High concentrations of acid can cause corrosion.
Alkaline Environment: Resistant to strong alkali (e.g. NaOH), but stress corrosion cracking (SCC) may occur in high temperature concentrated alkali.
1.4401 Stainless Steel Acid Resistance:Non-oxidizing Acid: Due to the presence of molybdenum, its corrosion resistance is significantly better than 1.4301; suitable for sulfuric acid/phosphoric acid processing (e.g. reactor vessels).
Alkaline Environment: Similar to 1.4301, but more stable in high temperature concentrated alkali.
2.3 High Temperature and Oxidizing Environment
1.4301 High Temperature Resistance: Short-term use temperature up to 870°C; long-term exposure (420-870°C) may cause carbide precipitation, resulting in intergranular corrosion, good oxidation resistance, suitable for general high temperature use (e.g. kitchen appliances).
1.4401 stainless steel high temperature resistance: wider temperature range (950°C for short term, 800°C for long term); excellent resistance to high temperature oxidation and sulfidation. Molybdenum can improve stability under severe thermal cycle conditions, making it suitable for heat treatment equipment and boiler components.
Through salt spray test and immersion experiment, it was found that 1.4301 showed obvious pitting after 30 days in salt spray environment, while 1.4401 had only slight rust on the surface. In the dilute hydrochloric acid immersion test, the corrosion rate of 1.4401 was 0.021 mm/year, which was much lower than 0.12 mm/year of 1.4301.
| Environment | Recommended Alloy | Rationale |
|---|---|---|
| Food processing/kitchenware | 1.4301 | Cost-effective, meets food-grade standards (e.g., FDA). |
| Marine/offshore | 1.4401 | Excellent seawater resistance, prevents chloride-induced pitting. |
| Chemical processing | 1.4401 | Resistant to acids/alkalis, especially Cl⁻-containing media. |
| Architectural decoration | 1.4301 | Low cost, good aesthetics after polishing. |
| High-temperature components | 1.4401 | Better creep resistance and oxidation stability at elevated temps. |
【1】Shunqi.com. (2025). 1.4401 stainless steel: detailed chemical composition and corrosion resistance analysis.
【2】QC Hydraulics. (no date). Which steel is stronger: AISI 304 or AISI 316.
【3】Journal Center of Shanghai Jiaotong University. (2024). Analysis of the causes and preventive measures of 316L stainless steel pipeline corrosion.
【4】Yuanta Stainless Steel Water Tank. (2025). How to choose between 304 and 316L stainless steel water tanks? Corrosion resistance test comparison report of material engineers.
【5】Jiusong Health. (2025). Is food grade 316 better or 304 better?
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