Stainless steel in sanitary areas: AISI 304 or AISI 316 — what's the difference?
"Stainless steel" is on the product description – but which stainless steel? In the sanitary sector, this question is crucial. Not every alloy is suitable for every environment. Those who choose the wrong material properties risk corrosion damage, increased maintenance costs, and in the worst case, premature replacement of the entire system.
This article explains the difference between the two stainless steel grades relevant in the professional sanitary sector – AISI 304 and AISI 316 – and shows when each grade is the right choice.
What "stainless steel" means – and what it doesn't
Stainless steel is not a single material, but a group of alloyed steels with a chromium content of at least 10.5%. The chromium forms a thin passive layer on the surface, which protects the steel from corrosion and regenerates itself independently if damaged.
Whether this protective effect is sufficient for the specific application depends on the exact alloy composition – particularly the molybdenum content. In the professional sanitary sector, two austenitic grades are decisive: AISI 304 and AISI 316.
AISI 304 – the proven standard (V2A / 1.4301)
The most widely used stainless steel worldwide. It contains around 18% chromium and 8–10% nickel – no molybdenum. It is well suited and economical for normal drinking water conditions and indoor applications with low chloride exposure.
Advantages: Good general corrosion resistance, easy to process and weld, wide availability, proven in millions of sanitary installations worldwide.
Limitations: Sensitive to chloride-containing media. In swimming pools, outdoor facilities, or with increased chloride content in water or, for example, in soaps, pitting corrosion can occur – often invisible until through-corrosion.
Typical use: Indoor facilities in schools, office buildings, administrative buildings, sports halls – wherever normal drinking water and no increased chloride exposure is present.
AISI 316 – the all-rounder for demanding environments (V4A / 1.4401 / 1.4404)
AISI 316 additionally contains 2–3% molybdenum. This addition significantly increases resistance to pitting and crevice corrosion in chloride-containing environments. The 316L variant (1.4404) has a lower carbon content – it is more suitable for welding and reduces the risk of sensitization corrosion at welds.
Advantages: Significantly higher chloride resistance, suitable for swimming pool facilities, outdoor facilities, outdoor showers, and medical environments. Preferred material for sanitary fixtures and fittings with elevated hygiene or corrosion requirements.
Limitations: Higher material price than AISI 304. In extremely aggressive media – such as seawater or heavily chlorinated baths with continuous contact – even higher alloyed grades are necessary.
Typical use: Hospitals, nursing homes, food processing facilities, swimming pools, outdoor facilities, correctional facilities, all facilities with elevated hygiene or corrosion requirements.
| Practical tip: The material designation according to European standard (1.4301 or 1.4401/1.4404) is clear. Trade names like "V2A" or "V4A" are useful abbreviations, but not a standard. When purchasing, pay attention to the specific material number or the AISI designation – not just the term "stainless steel". |
Comparison at a glance
| Property | AISI 304 (1.4301) | AISI 316 (1.4401/1.4404) |
| Chromium | ~18% | ~18% |
| Nickel | 8–10% | 10–12% |
| Molybdenum | — | 2–3% |
| Chloride resistance | Medium | High |
| Drinking water contact | Yes (normal conditions) | Yes (recommended) |
| Weldability | Good | Very good (316L) |
| Cost (relative) | Medium | Higher |
| Typical use | Indoor, normal conditions | Chloride, outdoor, medical, |
Surface: underestimated, but crucial
Not only the alloy, but also the surface finish significantly influences the corrosion resistance and hygiene of a fitting.
Polished (mirror finish): Very low roughness. Hygienically optimal – bacteria and dirt hardly adhere. Fingerprints visible, slightly more maintenance required.
Satin (brushed): Good compromise solution: sufficiently hygienic and less sensitive to visible signs of wear. The most common standard in public sanitary facilities.
Important: Surface damage – scratches from incorrect cleaning agents or improper installation – can locally destroy the passive layer and trigger corrosion. Even with high-quality material: care and proper installation are part of the product's lifespan.
| Practical tip: Use only chloride-free cleaning agents. Chloride-containing cleaners – even in low concentrations – can attack the passive layer and eventually lead to pitting corrosion. For professional care of stainless steel fittings, we recommend ASA-SLA 37 stainless steel cleaner and polish – seals and polishes the surface in one step. |
What to look for when procuring
In practice, one regularly encounters fittings labeled "stainless steel" without specifying the exact alloy. This makes evaluation considerably more difficult. When procuring, the following should be considered:
Request material designation: A reputable product description names AISI 304 or AISI 316 – not just "stainless steel" or "high quality".
Define environment: Indoor with normal tap water, or outdoor area, swimming pool, medical environment? The more aggressive the environment, the clearer the choice for AISI 316.
Consider material thickness: Especially for vandalism-proof fittings for correctional facilities or public high-traffic areas, material thickness is an independent quality feature – in addition to the alloy.
Stainless steel at Armatron
Armatron works exclusively with AISI 304 and AISI 316 – depending on the area of application and requirement profile. All fittings and sanitary fixtures are designed for continuous operation in public buildings, hospitals, schools, and security-critical facilities. No coatings that can peel off. No plastic parts in exposed areas.
Do you have questions about material selection for your project – for example, with increased chloride content, swimming pool environments, or high-security areas? We would be happy to advise you.
Conclusion
AISI 304 is the economical standard for normal conditions and has proven itself in countless indoor installations. AISI 316 is the right choice as soon as chlorides, aggressive cleaning agents, or increased hygiene requirements come into play. The surface finish also influences hygiene and maintenance effort during operation.
Those who pay attention to the specific AISI designation when purchasing, instead of just "stainless steel," make an informed decision – and avoid expensive surprises during operation.
If you have any questions about material selection for your sanitary installation, please feel free to contact us by phone at +41 44 825 62 62 or by email at info@armatron.ch.
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