Accelerated corrosion of pure Fe, Ni, Cr and several Fe-based alloys induced by ZnCl2–KCl at 450 °C in oxidizing environment

Corrosion problems in waste incinerators are usually rather severe, also due to the presence of low-melting point heavy and alkali metal chlorides. In this paper, the corrosion behavior of several Fe-based alloys with different Cr content, as well as three pure metals Fe, Cr, and Ni, was studied at 450 °C beneath ZnCl2–KCl deposits in flowing pure oxygen. All the materials suffered from accelerated corrosion characterized by an important separation and spallation of the oxide scales. The Cr-containing alloys did not exhibit better corrosion resistance to this environment due to the poor adherence of the scales to the matrix, while higher Ni content could improve the corrosion resistance. Chlorine was always enriched on the substrate surface beneath the scale, and in some cases chlorine-rich corrosion products were also present within the alloy matrix. For the HP heat-resistant steel, Cr-rich Cr7C3 carbides were preferentially attacked in comparison to the matrix. The effect of Cr is discussed with respect to the nature of the scales.