The corrosion rate of metals and metal coatings in atmospheric conditions is determined by the combined action of several factors: the presence on the surface phase and adsorption films of moisture, air pollution korrozionnoagressivnymi substances, changes in air temperature and the metal, the formation of corrosion products and other assessment and calculation of the corrosion rate should be based on the length and material the corrosive effects of the metal the most aggressive factors. Depending on the factors influencing the rate of corrosion, it is appropriate following division of the operating conditions of metals subjected to atmospheric corrosion: 1. Enclosed with the internal sources of heat and moisture (heated rooms), 2. Enclosed with no internal sources of heat and moisture (unheated rooms), 3. The open atmosphere.
On degree of exposure to metals corrosion protection should be divided into non-aggressive, slightly aggressive, and sredneagressivnye silnoagressivnye. To determine the degree of aggressiveness in atmospheric corrosion Wednesday must take into account the operating conditions of metal structures and buildings. The degree of aggressiveness of the environment in relation to structures within the heated and unheated buildings, buildings without walls and constantly aerated buildings defined by the possibility of moisture condensation, as well as temperature and humidity conditions and the concentration of gas and dust inside the building. The degree of aggressiveness of the environment in relation to structures in the open air, not protected from direct contact with precipitation, the climate zone and the concentration of gases and dust in the air. Taking into account the influence of meteorological factors and aggressive gases developed classification of the degree of aggressiveness of media in relation to the structural metal, which are presented in Table 1. Thus, the protection of metallic structures from corrosion is determined by the aggressiveness conditions of their ekspluatatsiiyu. The most reliable protective systems of metal structures are aluminum and zinc coatings.