Corrosion Behavior of Alloy 800 in Simulated Crevice Solutions

Corrosion behavior of alloy 800 in simulated steam generator crevice solutions was investigated by using potentiodynamic polarization, cyclic voltammetry, cyclic polarization techniques together with scanning electron microscopy and energy dispersive spectroscopy. The experimental results revealed that the passive range and pitting corrosion potential of alloy 800 in the solution containing both thiosulphate and chloride ions are lower than that in the solution with S2O32- or Cl- ion alonely or the combination of SO42- and Cl- ions, but the passive current density of alloy 800 in thiosulphate and chloride containing solution is the largest among the five simulated solutions. The passive film of alloy 800 in simulated crevice solution is mainly iron oxides and Cr2O3. The addition of Cl- and S2O32- ions in the solution could hinder the formation of passive film on alloy 800, and thus alloy 800 has a higher pitting corrosion susceptibility. Finally the pitting mechanism of alloy 800 in S2O32- and Cl- containing solution was discussed.