Abstract
Laboratory corrosion tests were conducted for austenitic stain-less steels and Ni-base alloys in a corrosion environment simulating waste incinerators at 400-550°C. Corrosion weight loss of steels and alloys depended predominantly upon the chemistry of ashes, corrosion temperature, and the alloy composition. For an ash of chloride mixture, Ni-base alloys had a minimal attack whereas for an equimolar mixture of chlorides and sulfates, the effects of alloy constituents such as Cr, Ni and Mo on corrosion depended on the corrosion temperature. At 550°C, corrosion rates of high-Cr steels and alloys were small, and addition of Mo reduced the corrosion considerably. For alloys of similar Cr content, Ni was rather a harmful alloying element for the corrosion. At 400°C, ashes of lesser chloride content became less corrosive, and high-Ni alloys such as 825 and 625 performed generally well.
The effects of Ni and Cr on corrosion were interpreted from the point of reaction between protective NiO/Cr2O3 scale and fused salts. An "apparent" acid-base chemistry was introduced for fused chlorides in order to understand the corrosion in this environment.
