Effect of Time and Temperature on the Sensitization on Alloy 600 by Electrochemical Potentiokinetic Reactivation

Abstract

This study investigated the effect of temperature and time on the sensitization behavior of alloy 600. A doubleloop electrochemical potentiokinetic reactivation test was conducted to evaluate the degree of sensitization (DOS) in 0.1 M H2SO4 + 0.001 M potassium thiocyanate solution. The microstructure and surface damages of the aged specimens were characterized by optical microscope, scanning electron microscope, and energy dispersive X-ray spectroscopy. As a result of the experiment, the sensitization behavior was significantly influenced by the expansion of the Cr-depleted zone and Cr-diffusion rate depending on the aging temperature. In particular, the alloy 600 aged for 300 h or longer at 650 • C represented a very low DOS value of 3% or less, and its resistance against intergranular corrosion greatly improved.