A subgroup of stainless steels, which has a particularly high resistance to many environmental influences that promote natural corrosion. Stainless steel is a concept of value which is based on the assumption that this material is resistant to most of the influences that occur in the normal atmosphere. The alloying element Cr (chromium) is decisive for these stainless steels, which are designated as high-alloy stainless steels.
A prerequisite for the formation of the so-called passive layer (chromium oxide/chromium hydroxide layer), which is only a few nm (nanometres) thick, in stainless steel is at least 10.5 mass % chromium, max. 1.2 mass % carbon, and the influence of oxygen and moisture from the surrounding atmospheric air. Contamination e.g. by salts (chlorides) and the lack of oxygen or moisture can greatly reduce the resistance, so that the so-called stainless steel does corrode again and forms brown rust.
If there is any uncertainty about the correct choice of material and the assessment of environmental conditions, an expert must always be consulted.
In such a case please contact the Informationsstelle Edelstahl Rostfrei in Düsseldorf, www.edelstahl-rostfrei.de.