Corrosion of Stainless Steel in NaCl-KCl Based Melts

Abstract

Corrosion behavior of stainless steel types AISI 316L, 316Ti and 321 was studied at 750 0 C in NaCl-KCl equimolar melts. Iron, chromium and manganese species constitute the major corrosion products. The following mechanism of stainless steel corrosion in molten chlorides was proposed: 1) chemical interaction between the alloy and the salt intensified by the formation of microgalvanic pairs; 2) formation of chromium and molybdenum carbidecontaining phases in steel as a result of heating to 750 0 C; 3) additional formation of galvanic pairs between the grains of austenitic alloys and the carbide phases at the grain boundaries resulting in enhanced intergranular corrosion.

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

“…Thus, less chromium oxide products will be formed on the grain boundary surface which may make the grain boundary more susceptible to dissolution compared to the grain itself. The sensitization effect on the corrosion in molten chloride media had been previously reported by Polovov et al [23] who studied the corrosion of austenitic stainless steel in molten NaCl-KCl salt. The resistance to intergranular corrosion was improved in the order of AISI 316L (< 0.03C, 2.2-2.8Mo, in wt%) > AISI 316Ti (< 0.1C, 0.5-0.7Ti, 2.0-3.0Mo, in wt%) > AISI 321 (< 0.12C, 0.5-0.8Ti, in wt%), due to the decreasing of the carbon content or increasing of the content of strong carbide forming elements.…”

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

“…Thus, less chromium oxide products will be formed on the grain boundary surface, which may make the grain boundary more susceptible to dissolution compared to the grain itself. The sensitization effect on the corrosion in molten chloride media has been previously reported by Polovov et al [30], who studied the corrosion of austenitic stainless steel in molten NaCl-KCl salt. The resistance to intergranular corrosion was improved in the order of AISI 316L (<0.03C, 2.2-2.8Mo, in wt%) > AISI 316Ti (<0.1C, 0.5-0.7Ti, 2.0-3.0Mo, in wt%) > AISI 321 (<0.12C, 0.5-0.8Ti, in wt%), due to the decrease of the carbon content or increase of the content of strong carbide-forming elements.…”

Corrosion behavior and mechanism of 316 stainless steel in NaCl–KCl–FeCl3 molten salt and vapor at 300°C

“…[1,2] Moreover, chloride salts have a serious corrosion attack on the structural materials due to hygroscopicity, which has a great impact on the overall performance of the TES system. Compared with the chloride salt, that is, NaCl-KCl, [3,4] LiCl-KCl, [5,6] NaCl-KCl-MgCl 2 , [7,8] NaCl-MgCl 2 , [9,10] KCl-MgCl 2 , [11,12] and NaCl-KCl-FeCl 3 , molten salts with good thermophysical properties have a lower melting point (~140°C) and lower cost, and thus serves as a candidate for heat transfer and storage material in the TES and concentrated solar power (CSP) system. [13,14] The corrosion of the structural materials in chloride salt is quite important and is cause for wide concern, as it is directly related to the lifespan of the structural materials, [9,[15][16][17][18] and in turn the safety of the whole system.…”

“…316 stainless steel (316 SS) alloy is one of the promising candidate materials for the next-generation CSP because of its low cost and relatively good corrosion resistance in chloride molten salt. [4,6,7,9,13,17] The major corrosion products of 316 SS alloy in the NaCl-KCl molten salt at 750°C are the Fe, Cr, and Mn species, and the carbon content of 316 SS alloy determines its corrosion resistance. [4] The corrosion mechanism of the 316 SS alloy in the LiCl-KCl molten salt at 600°C was the selective dissolution of Cr with the gradual formation of voids, and Cr compound on the alloy surface.…”

“…[4,6,7,9,13,17] The major corrosion products of 316 SS alloy in the NaCl-KCl molten salt at 750°C are the Fe, Cr, and Mn species, and the carbon content of 316 SS alloy determines its corrosion resistance. [4] The corrosion mechanism of the 316 SS alloy in the LiCl-KCl molten salt at 600°C was the selective dissolution of Cr with the gradual formation of voids, and Cr compound on the alloy surface. [6] Further studies conclusively showed that the corrosion mechanism of 316 SS alloy under NaCl-MgCl 2 molten salt is the combined effect of a dissolution mechanism with matrix metal elements at three different temperatures, 500°C, 600°C, and 700°C.…”