Comparative Study of Ni effect on the Corrosion Behavior of Low Alloy Steels in FGD and Acid Rain Environments

摘要

The alloying effect of a small amount of nickel on low alloy steel for application to flue gas desulfurization(FGD) systems was studied. The structural characteristics of the rust layer were investigated by scanning electron microscopy(SEM). The electrochemical properties were examined by means of potentiostatic polarization test, potentiodynamic polarization test, and electrochemical impedance spectroscopy(EIS) in a modified green death solution of 16.9 vol. percent H_2SO_4+ 0.35 vol. percent HCl at 60 deg C and an acid rain solution of 6.25 X 10~(-5) M H_2SO_4+5.5 X 10~(-3) M NaCl at room temperature. It was found that as the amount of nickel increased, the corrosion rate increased in the modified green death solution, which seemed to result from micro-galvanic corrosion between NiS and alloy matrix. In acid rain solution, the corrosion rate decreased as the amount of nickel increased due to the repulsive force of NiFe_2O_4 rust against Cl~- ions by electronegativity.