Pitting Corrosion of 12kh18AG18Sh Steel in Chloride Solutions

摘要

We experimentally established that the corrosionrate of l2Kh 18AG 18Sh steel In a 22percent NaCl solution inthe temperature range 20- l00deg C does not exceed 0.22g/(m~2 · h) (or 0.277 mm/year). The material undergoes self-passivation with the formation of a protective passive film ofFe_3O_4 + (Fe, Cr)_2O_3 + (Mn, Fe)_2O_3. Pitting resistanceof steel decreases in solutions with a concentration of chlorideions of above 0.2 mole/liter and temperatures of at least 40deg C.We studied selective dissolution of certain components of steeland found that manganese is most soluble. Ionization ofchromium occurs more slowly than that of the iron matrix. As aresult of selective dissolution of steel, the passive film isdepleted of manganese and nitrogen.