Chromizing was applied as a measure against corrosion of gas expander rotors due to high-temperature sulfidation. Both Waspaloy disk and blades of a gas expander rotor were chromized, after which fretting test and corrosion test were carried out to evaluate the usefulness of the
chromizing. Favorable test results were obtained. High-temperature sulfidation corrosion is a problem which involves not only gas expanders but also various energy conversion machinery, such as turbine and boilers, which are operated in high temperature environments with sulfuric compounds. The measure developed, featuring chromizing, is expected to be utilized in various industries as a safeguard against this problem.