304 and 316 are both austenitic chromium-nickel stainless steels, and on paper their mechanical properties — tensile strength, hardness, ductility — are close enough that buyers often default to whichever is cheaper or more readily available. The meaningful difference is chemical, not mechanical: 316 adds 2–3% molybdenum to the alloy, which significantly improves resistance to pitting and crevice corrosion in chloride-rich environments.
When 304 is the right call
304 (and its low-carbon variant, 304L, which resists weld-decay better) covers the large majority of general engineering, architectural and food-contact applications — kitchen equipment, structural fasteners, indoor fabrication, dry or mildly humid environments. It is more readily available, faster to machine, and typically 15–25% cheaper than 316 for the same section.
When to specify 316
316 (and 316L) is the standard choice wherever the material will see chlorides — coastal installations, marine hardware, chemical processing, pharmaceutical equipment, and anything regularly exposed to cleaning agents or saline atmosphere. The molybdenum addition also gives 316 a modest edge in high-temperature strength, which is why it shows up in process piping and pressure equipment specs even away from the coast.
A practical rule of thumb
If the finished part will be washed down, submerged, or sited within a few kilometres of a coastline, specify 316. If it stays dry and indoors, 304 will perform for the design life of the product at a meaningfully lower material cost. When in doubt, send us your end application — grade selection is one of the most common calls our metallurgical team fields, and getting it right the first time avoids a costly re-order.
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