The Onset of Potassium Chloride Induced High Temperature Corrosion: A Novel Experimental Approach
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The present study investigates the early stages of the oxide layer degradation process of Sanicro 28 (Fe31Cr27Ni) stainless steel when exposed to KCl at 450 and 535 °C. A novel combinatory technique was developed and utilized, where CA was employed as a qualitative method to follow the varying stages of the onset of the corrosion reaction. XPS was then used to identify the elemental distribution and depth profile within the oxide layer at each identified reaction stage, and the resulting change in surface morphology and the progress of the corrosion front was studied by SEM-EDXA. Additionally, the main mechanism behind the spreading of the reaction front was identified using a novel test approach. The corrosion reaction could be separated into several overlapping stages, with the process being initiated by the alternation of the oxide layer resulting in the loss of passivity, the formation of chromate within the oxide layer and finally the oxidation of the chromium and iron from underlying material.
KeywordsKCl Sanicro 28 Chronoamperometry High-temperature corrosion K2CrO4
The author would like to thank Mr. Linus Silvander for operating the SEM-EDXA apparatus and Mr. Jyrki Juhanoja from Top Analytica Oy Ab for operating the XPS apparatus. This work has been carried out within FUSEC (2011–2014) as part of the activities of the Åbo Akademi Process Chemistry Centre. Other research partners are VTT, Lappeenranta University of Technology, Aalto University and Tampere University of Technology. Support from the National Technology Agency of Finland (Tekes), Andritz Oy, Metso Power Oy, Foster Wheeler Energia Oy, UPM-Kymmene Oyj, Clyde Bergemann GmbH, International Paper Inc. and Top Analytica Oy Ab is gratefully acknowledged.
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