Abstract
The reaction rate of cobalt in 
environments has been measured at 650°, 700°, 750°, and 800°C. Product scales consist primarily of an interconnected sulfide phase in an oxide matrix. At all temperatures, the rapid diffusion of cobalt outward through the interconnected sulfide appears to be important. At 650°C, the reaction rate slows dramatically after 5 min due to a change in the distribution of these sulfides. At 700° and 750°C, the reaction is primarily diffusion controlled; values of 
calculated from this work show favorable agreement with values of 
calculated from previous sulfidation work. At 800°C, a surface step becomes rate limiting.