Match the Grade to the Environment
Choosing the correct stainless steel is crucial to avoid premature failure. CNB provides metallurgical guidance to help you select the optimal grade based on corrosion resistance, strength, and cost.

Grade Selection Logic

• Atmospheric Exposure (Rural/Urban): 304/304L – Good for general use. Avoid heavy industrial pollution (SO₂) without regular cleaning.

• Coastal/Marine: 316L (PREN ≥ 24) is minimum for within 5 km of the sea. Duplex 2205 (PREN ≥ 34) for splash zone and seawater handling.

• Chemical Processing: 316L for many acids; 904L (PREN ≥ 43) for sulfuric acid service. Refer to iso‑corrosion curves.

• High Temperature: 310S for oxidation resistance to 1100°C. 321 for stabilized grade against intergranular corrosion in 425‑815°C range.

• Food & Beverage: 304L for dry or cold. 316L for chloride‑containing cleaning solutions. Electropolished finish for hygiene.

Understanding PREN (Pitting Resistance Equivalent Number)
PREN = %Cr + 3.3(%Mo) + 16(%N). Higher PREN indicates better resistance to pitting corrosion. For example, 304 PREN ~19, 316 PREN ~25, 2205 PREN ~34.