Stainless steel is an alloy mainly composed of iron and chromium.
The addition of 12% to 20% chromium forms a protective layer that prevents rust. An additional amount of nickel further improves corrosion resistance and makes the steel austenitic (non-magnetic).
On the market, several food-grade stainless steel series exist, according to the American AISI standard:
- Series 200 (AISI 201, AISI 202, …): at least 12% chromium and around 2% nickel.
- Series 300 (AISI 304, AISI 316, …): up to 18% chromium and 10% nickel.
- Series 400 (AISI 430, AISI 441, …): up to 18% chromium, without nickel.
Series comparison:
- Series 200 offer the weakest protection against corrosion. Although austenitic, they are not reliable in culinary environments and are mainly used in the Asian market.
- Series 300 offer the best protection. Stainless steel AISI 304, in particular, is suitable for most food, pharmaceutical, laboratory, and decorative applications, with the exception of highly demanding environments such as maritime, surgical, or cleanroom use.
- Series 400 are a good compromise. Stainless steel AISI 430, while magnetic, provides very good corrosion resistance for traditional food use. However, it should be avoided in sensitive environments such as fish shops, butcheries, or coastal areas.