Definition
AISI 304 and AISI 316 are the two most-used austenitic stainless steel grades worldwide. Both are non-magnetic chromium-nickel alloys engineered for corrosion resistance and formability. They look identical, finish identically, and machine almost identically. The decisive difference is molybdenum, 316 contains 2-3% Mo, 304 contains essentially none, and that single addition shifts pitting and crevice corrosion resistance enough to make 316 the default in chloride-rich marine and coastal environments and 304 the default everywhere else.
Chemistry and EN designations
304 (EN 1.4301, UNS S30400): C ≤0.07%, Cr 17.5-19.5%, Ni 8.0-10.5%, Mn ≤2.0%, P ≤0.045%, S ≤0.03%, N ≤0.10%.
316 (EN 1.4401, UNS S31600): C ≤0.07%, Cr 16.5-18.5%, Ni 10.0-13.0%, Mo 2.0-2.5%, Mn ≤2.0%, P ≤0.045%, S ≤0.03%, N ≤0.10%.
The molybdenum and slightly higher nickel deliver superior pitting resistance, particularly in warm chloride solutions, exactly the service condition created by GCC coastal humidity, salt-laden air and sea-spray exposure.
Mechanical properties
Property | 304 | 316 0.2% proof stress | ≥210 MPa | ≥220 MPa Tensile strength | 520-720 MPa | 530-680 MPa Minimum elongation | 45% | 40% Hardness (HB) | ≤215 | ≤217 Density | 7.93 g/cm³ | 7.98 g/cm³ Thermal conductivity | 16 W/m·K | 16 W/m·K Coefficient of thermal expansion | 17.3 µm/m·K | 16.0 µm/m·K
Corrosion resistance
PREN (Pitting Resistance Equivalent Number) = Cr + 3.3×Mo + 16×N. 304 PREN ≈ 18-20 (typical). 316 PREN ≈ 24-26 (typical).
For chloride pitting resistance, PREN above 24 is the threshold for confident service in coastal and marine environments. 304 will pit in standing seawater and in chloride-laden coastal atmospheres within months; 316 stays bright for years to decades.
In industrial atmospheres with chemicals or chlorides, in food and beverage processing, in pharmaceutical and medical service, and in chemical handling, 316 is the standard. In general architectural, kitchenware, food contact (non-aggressive), and dry industrial service, 304 delivers identical aesthetics at materially lower cost.
Cost comparison
316 typically prices 25-40% above 304 on a per-tonne basis, driven by the molybdenum and higher nickel content. Nickel and molybdenum surcharges fluctuate with LME prices, so the gap can widen to 50% during nickel cycles or narrow to 18% in soft markets. For most GCC architectural projects the cost differential is meaningful enough that 304 is specified for interior and inland service while 316 is reserved for coastal exposure.
Where each grade wins in the GCC
Use 316 for: Coastal architectural facades (Palm Jumeirah, Bluewaters, Yas Island, Lusail, AlUla, NEOM coastal). Marine handrails, balustrades, marina structures, boatbuilding hardware. Kitchen and food processing equipment in salty or acidic service. Desalination and water treatment plant fittings. Chemical and pharmaceutical process equipment. Fasteners and fittings in coastal high-humidity service.
Use 304 for: Interior architectural fit-out across UAE, KSA, Qatar (away from direct sea exposure). Kitchen sinks, hospital surfaces, food service (non-aggressive). General fasteners, decorative balustrades, signage frames. Industrial equipment in dry inland service. Light chemical and process service without chlorides.
On the line between the two, Burj Al Arab perimeter, Doha Corniche balustrades, Jeddah Corniche, consultants typically specify 316 for the corrosion budget.
Specification language
"Stainless steel sheet AISI 304, 2B finish, 1.5mm x 1250mm x 2500mm, to ASTM A240" or "Stainless steel pipe AISI 316L, ASTM A312, sch 40, seamless", these are the unambiguous specification lines used on GCC tenders.
When the EN reference is preferred, swap to "1.4301" (304) or "1.4401" (316). The grade naming systems are interchangeable on dual-certified MTCs.