The surface of steel is very sensitive to action of many chemical substances as well as the industrial atmosphere or the natural atmospheric agents. In case of acid or alkali acting on the steel occur the reaction which results that the steel is digesting within a short time, especially when media are mixed. Only in some cases there appears the passivation of steel and the reaction is repressed.
In the industrial atmosphere or under the influence of atmospheric agents (air, water, acid rains, industrial vapours) follows the gradual corrosion of steel, which last until processing all the mass of steel into the rust. This is because the rust is not a safety fence and corrosion factors in the easy way penetrates underneath, causing the further progression of corrosion.
In atmosphere of chemical vapours e.g. galvanizing plants, just after one year of exploitation and even on stainless steel (rustless) there appears first indications of corrosion. Unprotected steel starts to lose the mechanical properties. The dropping off rust makes up the potential danger of production purity, and in case of tanks makes up the danger of media effluent, as a result of tank walls perforation, which can appear in a very short time.