Corrosion Behavior of Structural Materials in LiCl-KCl Molten Salt by Thermogravimetric Study

Abstract

Spent metallic fuel from future fast-breeder reactors would be processed by non-aqueous pyrochemical reprocessing. Different unit operations of pyrochemical reprocessing demands various structural materials that are compatible with molten salt medium at high temperatures. In the present study, the corrosion behavior of the candidate materials stainless steel (SS) 410, alloy 600 and 9Cr-1Mo (9% chromium and 1% molybdenum) steel was investigated in molten lithium chloride-potassium chloride (LiCl-KCl) salt by thermogravimetric studies under inert and reactive atmospheres. The test specimens, along with molten salt, were isothermally heated at 500 and 600°C for 24 h in both atmospheres. Alloy 600 showed marginally higher weight gain than 9Cr-1Mo and SS410 under both atmospheres at 600°C. Higher weight gain was observed under reactive atmosphere than in inert atmosphere at 600°C. All of the samples investigated under both atmospheres at 500°C showed insignificant weight loss. The surface morphology and energy dispersive x-ray spectroscopy (EDS) analysis revealed the formation of porous corrosive layers all over the surface with Cr-depleted and Cr-rich regions. The laser Raman spectroscopy (LRS) analysis confirmed the formation of a lithium chromite (LiCrO 2 ) layer in all the alloys and formation of iron (Fe) and Cr oxides along with spinel peaks. The attack by molten salt was observed to be more in 9Cr-1Mo steel than in SS410, followed by alloy 600 under both atmospheres.

High temperature molten salt corrosion of structural materials in UCl3–LiCl–KCl

“…As evidenced from this study and previous studies in molten chloride salts [7,9], the corrosion of alloys was higher at elevated temperatures and under reactive atmosphere. The molten salt corrosion of alloys follows as initially, the alloying elements would form the corresponding metal chlorides.…”

“…This technique is more appropriate, useful and provides in-depth insights about the corrosion processes occurring in-situ on the alloy surface. Authors [7,9] also previously used the thermogravimetric technique to evaluate the corrosion behaviour of structural materials in eutectic LiCl-KCl salt under Ar and Ar + 10% O 2 atmosphere at high temperatures that indicates the attack by molten LiCl-KCl salt was less in alloy 600 than SS 410 followed by 9Cr-1Mo steel in both inert and reactive atmospheres for 24 h duration. The corrosion behaviour of candidate structural materials in UCl 3 -LiCl-KCl molten salt at 500°C and 600°C studied using thermogravimetry for about 6 h duration.…”

“…In our laboratory, the corrosion behaviour of various structural materials and coatings in molten salt under various atmospheres has been evaluated and reported [7 12]. Several authors have also reported the corrosion behaviour of different materials in molten salts for different applications [13 17].…”

Corrosion Behavior of Commercial Alloys in LiCl–KCl Molten Salt Containing EuCl3

“…As the formation of the protective oxide layer on the alloy surface is challenged in molten chloride media, the structural alloys used for the construction of an electrorefiner may suffer corrosion attack during its design life (e.g., 40 years). To screen the candidate alloys, several studies have evaluated the corrosion resistance of commercial alloys in LiCl-KCl molten salt (Shankar et al, 2010;Shankar et al, 2013a;Shankar et al, 2013b;Rao et al, 2015). In general, alloys exhibit preferential dissolution or oxidation of the active element Cr, which is induced by impurities such as moisture and oxygen in the molten salt.…”

Corrosion Performance of Commercial Alloys and Refractory Metals in Conditions for Electrorefining of Spent Nuclear Fuels

“…The presence of dissolved actinide and fission products during the electrorefining can also accelerate the dissolution kinetics of alloy elements in the molten salt electrolyte [3][4][5]. There are only very limited studies that have investigated the corrosion resistance of existing alloys in molten LiCl-KCl salts [6][7][8][9]. Most of these studies deduced that corrosion rate only becomes pronounced in reactive atmosphere.…”