Role of nitrogen in the active–passive transition behavior of binary Fe–Cr alloy system

Abstract

N effect on the active-passive transition behavior of Fe21Cr(0, 4)N (at%) alloys was investigated in sulfuric acid and borate-phosphate buffer solutions over a wide range of pH. The active-passive transition was observed only in a strong acid solution with a lower pH level than 2 regardless of the solution types. Alloyed N elevated a passivation potential of the FeCr matrix due to the strong Cr-N bonding formation in the matrix, thus, critical dissolution current density value was observed to increase. In the solution condition above pH 3, more protective passive film with higher Cr content was already formed on N-bearing alloy below the corrosion potential, thus the Fe oxidation current density appeared to be reduced. (C) 2012 Elsevier Ltd. All rights reserved.