Impact of Deposits and Their Morphology on the Active Corrosion of Iron in Chlorine- and Sulfur-Containing Atmospheres in the Temperature Range of 350-500 °C

L. Krumm, M.C. Galetz

Iron-based alloys have shown high corrosion rates under ash deposits typical for waste-to-energy plants. The ashes on superheater tubes in waste incineration are multicomponent systems including alkali and alkali–earth chlorides and sulfates. Under and within such salts, the corrosive effect on the alloy is induced by a complicated interplay of such ash products. On the one hand, in chlorine-containing atmospheres iron-based alloys are believed to be attacked by the so-called active corrosion, including the formation of volatile corrosion products and their transformation into stable iron oxides. At the same time, they form complex scales, involving among other compounds iron sulfides, chlorides, and oxides. Thus, in order to directly investigate the influence of a deposit on the corrosion in waste-to-energy plants and to reproduce the scales observed on field tested superheaters, this work compares the scale formation and metal wastage under different chemically inert alumina deposits with different grain sizes to a synthetic salt as well as to an actual deposit taken from a superheater tube in a plant.

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