Influence of MgCl2 content on corrosion behavior of GH1140 in molten NaCl-MgCl2 as thermal storage medium
As a thermal energy storage medium (TESM) at moderate-high temperature of concentrating solar power (CSP), the molten NaCl-MgCl 2 has sharp corrosive action on a metal container. The influence of MgCl 2 content on a metal corrosion behavior is not clear. The corrosion behavior of a Fe based alloy (GH1140) in molten NaCl-MgCl 2 (at 1123 K) with different content of MgCl 2 (wt%：0.0，48.9，61.0，93.6) were studied by the submergence corrosion experience. Results show that: after corrosion for 5 h, there is a negative correlation between the weight loss of samples and the content of MgCl 2 . In the molten salt without MgCl 2 , the sample was corroded according to the mechanism of “dissolution as anode- oxidizing- peeling off of oxide film”. After adding a little MgCl 2 in the molten salt , an unprotected MgO shell was formed on the sample surface. The samples weight decreased and obeyed a line law. The elements of Fe and Cr deplete in the corrosion layer. Corrosion mechanism is “dissolution as anode- oxidizing- reduction- chlorination”. When the content of MgCl 2 is very high in the molten salt, partial pressure of Cl 2 increases. The corrosion mechanism is similar to what in the molten salt with a little MgCl 2 , but the chlorination reaction is more severe.
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