Korozijski postojani čelici (nehrđajući čelici, Inox čelici)
Corrosion consistent steel (stainless steel, Inox steel)
Corrosion is the degradation of materials' properties due to interactions with their environments and medium such as gases, liquids or firm aggressive particles, and due to chemical or electrochemical processes.
Chemnical corrosion develops due to the influence of hot and dry air and gases or nonelectrolytes such as for example, bezine or acetone, onto the surface of steel, which leads to chemical reactions, mainly oxidation (e.g. FeO, Fe2O3 and Fe3O4).
Electrochemical corrosion is facilitated by the existence of electrolytes (conductive liquids or wet gases) under which the corroded metal acts as an anode and enters the solution in the form of ion. The electrochemical process appears when there is a difference between electrode potential of two short-circuited galvanic cells, e.g. two different metals in an electrolyte, different microstructural constituents or non-homogenous metal structure.
Resistance to corrosion is the ability of material to resist the interactions with its environment. More resitant to corrosion is material in which, under equal external conditions, there exists a less intense depredation on the surface or unwelcome changes in microstructure. Resistance to corrosion is determined and measured through: loss of M weight (thickness) and volume, changes of mechanical and other attributes during the corrosion effect, detection of surface damage or structural changes in the cross-section, as well as other ways. In practice, different ways of protection from corrosion are combined:
Corrosion resitant steels are alloys of iron with chrome (Cr) and nickel (Ni) and other alloying elements such as: molybdenum (Mo), wolfram (W) and titanium (Ti). Low content of carbon makes them resistant to corrosion.
(<0,25% C), high content of chrome (up to 30% Cr) and mono-phase structure (ferrite, austenitic, martensitic).