AISI 304 (Stainless Steel)

AISI 304 is an austenitic stainless steel containing roughly 18% chromium and 8% nickel, and it is among the most widely used stainless grades in manufacturing. The chromium forms a thin passive oxide layer on the surface that protects the material from oxidation and re-forms by itself after scratching. In wellness construction, AISI 304 is used for parts that are not in permanent contact with chemically treated water – structural brackets, frames, steel bands around wooden tubs, steps, handrails and fixings. Unlike AISI 316 it contains no molybdenum, so its resistance to chlorides is lower. In an environment free of chlorine and salt, however, it offers comparable service life at a lower cost.

Benefits of AISI 304 stainless steel

• Sound balance of durability and cost: For parts outside permanent contact with treated water it gives protection comparable to more expensive grades.
• Self-repairing passive layer: After mechanical scratching the protective oxide layer re-forms on the surface without intervention.
• Good weldability and formability: The material can be bent, welded and polished, which simplifies the manufacture of bespoke structural parts.
• Stable surface appearance: Both brushed and polished finishes keep their look over time in dry, non-chlorinated conditions.

AISI 304 and AISI 316: when 304 is enough

The difference between the two grades is molybdenum. Without it, AISI 304 is more sensitive to pitting corrosion, which is triggered by chlorides from chlorinated or salt water. The decision therefore does not rest on which steel is more resistant, but on what the part will actually be exposed to.