*2.2.3.4 Corrosion*

Corrosion may occur on the grounds of gypsum areas and in the immediate vicinity of them, and in structures (**Figure 5b**). In particular, there is a corrosive effect on installation, building foundation, and substructures. It leads to rapid deterioration, and rusting and corrosion of materials in buildings and substructure pipe systems. Underground corrosion results from chloride (Cl) dissolved from the evaporite units in the caves in the soil, sulfate salts (SO4), and dissolved gaseous oxygen (O). As a result of the fact that these dissolved ions cause stress difference in metal and electrolyte, they are oxidized to the metal ion in the anode or realize the corrosion (on the micro- or macroscale) event by passing into the solution as a metal ion [39]. Therefore, corrosion is one of the environmental problems arising from the gypsum unit since it causes damage to structures, building systems, and soil.
