The key distinction lies in molybdenum content, critical for corrosion resistance:
304 (ASTM A276; EN 1.4301; JIS SUS304): Contains 18–20% chromium, 8–10.5% nickel, and no intentional molybdenum. This balances cost and performance for general use (food processing, architecture).
316 (ASTM A276; EN 1.4401; JIS SUS316): Adds 2–3% molybdenum, enhancing resistance to chloride corrosion (e.g., seawater, deicing salts). It also has higher nickel (10–14%) for improved ductility.
Both grades resist oxidation up to 870°C, but 316's molybdenum reduces pitting in 5% salt spray by 70% compared to 304. This makes 316 preferred for marine hardware (bolts, shafts) and chemical plants, despite a 20–30% price premium.