The core difference between 304 and 316L is that 316L contains 2-3% molybdenum, giving it markedly stronger resistance to pitting and crevice corrosion; its price is typically 15-30% higher.

Scenarios where 316L is mandatory: exposure to chloride ions (coastal atmosphere, seawater, chlorine-containing cleaning agents), inability to perform adequate solution annealing after welding, hygienic piping for food/pharmaceutical applications, and concealed works where maintenance costs are high.

Scenarios where 304 can remain adequate: dry indoor environments, chloride-free media, and cost-sensitive decorative and structural components.

How to decide: first quantify chloride concentration and temperature, then check whether welds and crevices exist, and finally compare 10-year maintenance costs rather than looking only at the price per ton.