On contrary to chloride cracking, the caustic cracking occurs without oxygen, and small displacement of electrode potential into the area of Fe and Ni activity results in activation of selective dissolution of Fe and Ni with the two-stage formation of HFeO₂ and HNiO₂ ions and evolution of hydrogen ions. The hydrogen, evolved during the hydration of metal ions, diffuses into steel bulk in all causes of SCC. As the result steel in the tip of concentrators and microcracks is transformed into three- dimensional state of stress and the fracture energy decreases.

The stress corrosion cracks in this material may be initiated at regions of intensive local corrosion with high level of strain even if the metal surface film remains practically continues.

The pH potential at these sites differ from those in the bulk solution. They are determined by the reactions of the selective solubility of elements, metalloids and other phases of alloy. The possibility of definite reactions in the local region is determined on the basis of thermodynamic parameters of substances ( ST^O, CP^O, GT^O ), pH and potential. Information on the alteration of pH and potential at the local surface defect and activated sites is obtained from direct measurements of pH, from experiments alloying to separate anolyte from catholyte and to simulate partially the microdefect.