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

Abstract

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.

Deposit Shedding in Biomass-Fired Boilers: Shear Adhesion Strength Measurements

“…As a result, corrosion products, such as Fe/Cr chlorides, oxides, chromates, etc. are formed [2,5,6,7,8,9]. Most of the corrosion products form a complex eutectic mixture with the components present in the deposit [10].…”

“…Several corrosion studies in literature indicate that the rate of corrosion decreases considerably over time [2,5,12]. The change in melt fraction brought about by increasing corrosion is probably not significant enough to observe reliable changes in adhesion strength.…”

Experimental determination and thermodynamic optimization of the CuCl–ZnCl2, ZnCl2–FeCl3, CuCl–FeCl3, CuCl–CuCl2, FeCl2–FeCl3, FeCl2–CuCl2 and CuCl–PbCl2 phase equilibria

“…), a highly destructive fluxing of Cr2O3 scales. [35,38,40,41,43,48,73,87] Where the sulphate scale was thick and dense, it also prevented chromium vaporisation and instead, CrCl3/Cr2O3 scale was found beneath the sulphate scale.…”

Danish Experiences in Biomass Corrosion and Recent Areas of Research

“…The coupled effect of 40% H 2 O + 5% O 2 in the gas phase and small amounts of KCl deposit on stainless alloys at 600°C was investigated by [10,11] focusing on the mechanism of breakdown of the protective oxide by potassium to form potassium chromate. Sui et al 12 used chronoamperometry together with XPS (to distinguish Cr 3+ and Cr 6+ in the corrosion product) thus revealing that the formation of potassium chromate on UNS N08028 steel already occurred in the first 3 minutes of reaction at 450°C and 535°C. More recently, the use of O 18 to label different oxygen species in the gas phase (H 2 O and O 2 ) indicated that when KCl is present, oxygen from O 2 contributes primarily to the formation of chromate 13 .…”