Effect of Chloride Content in Ash in Oxidation Kinetics of Ni-Based and Fe-Based Alloys

Corrosion under deposit is one of the main mechanisms responsible of degradation and failure observed on heat exchangers in waste-to-energy plants. In this study, two heat exchanger materials, a low alloy steel (16Mo3) and a nickel-based alloy (Inconel 625) were isothermally exposed in air to two different synthetic ashes with low and high chloride contents at temperatures between 450 and 650 °C in a muffle furnace. After the test, thickness and mass losses were evaluated on two separate samples and metallographic cross sections of the specimens were characterized with a SEM/EDS analyzer. Results were in good agreement and have shown that the corrosion rates of both materials increase with chloride content especially for the ferritic steel. Additionally, it has been observed that corrosion rates increase above the temperature of solidus of salt mixtures, and thus, with the apparition of molten phase.