304 vs 316L：什么时候必须选 316L

Short answer: use 304 for indoor, low-chloride and decorative parts; switch to 316L when chlorides are present, when service is continuously above about 60 °C in a chloride-bearing medium, or for welded marine and chemical equipment. 316L contains 2–3% molybdenum, which resists pitting and costs roughly 30–40% more than 304.