REACTIONS BETWEEN GAS-PHASE, DEPOSITS AND METALLIC MATERIALS IN CHLORINE-CONTAINING ATMOSPHERES

Laboratory experiments were carried out in simulated waste incineratio n atmospheres at 500 degrees C on 2.25Cr-1Mo-steel covered by deposits . In He-5 vol.% O-2 enhanced corrosion takes place due to the formatio n of chlorine from the reaction of chlorides in the deposit with the o xide scale of the material. The Cl-2 diffuses through cracks and pores of the oxide scale and FeCl2 is formed at the metal/scale interface. By evaporation and outward diffusion through the oxide scale, FeCl2 ox idizes to Fe2O3 ('active oxidation'). In He-5 vol.% O-2-500 vppm HCl c atastrophic corrosion occurs; the sulfates in the deposits are convert ed to (K, Na)Cl and heavy metal chlorides (PbCl2, ZnCl2). Additions of SO2 (1000 vppm SO2) retards the corrosion process due to stabilizatio n of the sulfates in the deposits. Experiments on 2.25Cr-1Mo and Fe-32 Ni-27Cr (AC 66) covered with PbCl2 indicates a deleterious effect of h eavy metal chlorides on the corrosion process.