304 is an 18%Cr-8%Ni austenitic stainless steel with the best balance of workability, weldability, and cost, making it suitable for indoor decoration, kitchenware, general storage tanks, and normal atmospheric environments. 316L adds 2–3% molybdenum (Mo) to the 304 base, significantly improving resistance to pitting and crevice corrosion, and is especially suited to coastal high-salt-fog conditions, chloride-containing media, chemical piping, and food and pharmaceutical equipment; the L stands for low carbon (≤0.03%), which reduces the risk of weld sensitization. Selection sequence: first assess the chloride concentration in the environment and whether standing water can accumulate, then consider the medium temperature and welding requirements, and finally cost. In normal environments with no chloride exposure, 304 offers better value; where conditions are uncertain or involve long-term damp, salt-containing conditions, going directly to 316L is the safer choice.