The Onset of Potassium Chloride Induced High Temperature Corrosion: A Novel Experimental Approach

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 A degrees 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.