Abstract
To simulate corrosion of superheater tubes in waste incinerators, the effects of gas mixtures of Cl2-O2 and HCl-O2-H2O and KCl deposit on corrosion of C1010 low carbon steel at 400°C were examined by using thermogravimetric analysis. In 0.2/0.5/2%Cl2-1%O2-bal.Ar, accelerated corrosion occurred, and followed by mass decrease. In 0.2%Cl2-1%O2-bal.Ar, the top layer of scale was Fe3O4, which had a different morphology from that produced in environments without KCl, and beneath the Fe3O4 layer more K and Cl was detected. Accelerated corrosion would be hot corrosion by molten eutectic salt of KCl and FeCl2, produced by chlorination of iron. Fe3O4 would be precipitated from the molten salt because of higher oxygen potential at the gas/scale interface than the metal/scale interface. Volatilization of chloride would be the reason for the mass decrease. In 0.2%HCl-1%O2-2%H2O-bal.Ar, accelerated corrosion did not occur. However, by eliminating O2 from the gas system, accelerated corrosion was seen. The main corrosion product was Fe3O4. The accelerated corrosion could also be explained by hot corrosion by KCl-FeCl2 molten eutectic salt. It did not occur in 0.2%HCl-1%O2-2%H2O-bal.Ar probably because the chlorine potential was too small to produce enough FeCl2.
