Abstract

The effects of KSCN addition and its concentration on the reactivation behavior of sensitized Alloy 600 in an H 2SO 4 solution were investigated. Single-loop electrochemical potentiokinetic reactivation (SL-EPR), potentiostatic and potential decay tests were conducted in H 2SO 4+KSCN solutions, including intermittent adjustment of the electrolyte composition and concentration. The SL-EPR results showed that the maximum current densities of the reactivation peaks increased with an increase in KSCN concentration from 0 to 0.05 M in the 0.5 M H 2SO 4 solutions. A decrease in the peak current density was observed, however, if the KSCN concentration was increased to 0.5 M. The potentiostatic test results at +400 mV SCE showed that sensitized Alloy 600 could be passivated in plain H 2SO 4 and KSCN solutions as well as in mixed H 2SO 4+KSCN solutions. Potentiostatic tests at +30 mV SCE revealed that the presence of low KSCN concentrations made the passive film less stable in H 2SO 4 solutions, but it enhanced passivation at 0.5 M. The adsorption and desorption of SCN − and its subsequent redox reaction at different concentrations was discussed in relation to the reactivation of passive film formed on sensitized Alloy 600.

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