Stainless steels are Iron, Chromium and Carbon based alloys, possibly containing other elements like Nickel, Molybdenum, Silicon, Titanium, etc.
They are described as stainless because, in the presence of an oxidising environment (which could also be air), a protective layer made up of adsorbed Oxygen forms on their surface.
This invisible layer forms a barrier against the continuation of oxidation and, therefore, of corrosion. In order for this protective layer to form, a sufficient quantity of Chromium is indispensable. Euronorm 88-71 defines stainless steels as those ferrous alloys which contain at least 11% Chromium.
In relation to their structural behaviour, stainless steels may be divided into three basic categories:
• Martensitics, with a structure that varies according to temperature and can, therefore, be hardened by heat-treating. The characteristic types contain about 13% Chromium and small quantities of other elements in alloy, such as Nickel, in quantities that never exceed 2.5%.
• Ferritics, with a stable ferritic structure regardless of the temperature. The characteristic types contain about 17% Chromium and very low levels of Carbon, usually less than 0.1%.• Austenitics, with a stable austenitic structure regardless of the temperature. The characteristic types contain about 17% Chromium and Nickel in quantities greater than 7%.
Zamet S.p.A. stainless steel trunking and cable trays are widely used in the food, naval, road tunnel, chemical, pharmaceutical and animal breeding industries.