CORROSION OF CHROMIUM-CONTAINING ALLOYS IN NONSTEADY STATE ENVIRONMENTS CONTAINING OXYGEN, CARBON, AND CHLORINE

Internal attack of chromium containing alloys in mixed oxygen-chlorine environments occurs by the formation of pores which penetrate down gr ain boundaries of the alloys. No internal attack was detected in a bin ary Fe-20 %Cr alloy at 1200 K in environments containing 2500 ppm Cl2. The rate of internal attack of alloy 800H in such environments was in creased by replacing the O2 in the gas by CO2. In mixed oxygen-carbon- chlorine environments, the internal attack occurs by selective chlorin ation of chromium carbides which precipitate along the grain boundarie s.