Molten salts corrosion reactions

Impedance spectroscopic measurements are randomly used in molten salt corrosion studies. In general, most of the impedance spectra emphasize diffusion-controlled kinetics for the active corrosion of metals in molten salts. This behavior is expected, as the activation energy for charge-transfer reactions is easily reached at higher temperatures. 

Vanadium in a fuel forms various metal compounds with low melting points, and causes molten-salt corrosion of steel called vanadium attack. Another example of high temperature corrosion is sulfidation. Carbon monoxide, carbon dioxide, and hydrocarbons form metal carbides at high temperatures and this is called carburization. Nitriding involves chemical reaction of nitrogen with metal. 

Electrochemical cells can also be used to attempt to obtain data on the mechanisms of the salt-induced corrosion processes. Cyclic voltammetry has been used [78-22] to obtain information on the oxidation and reduction reactions that may occur during molten salt corrosion. Chronopotentio-metric investigations with platinum as the working electrode in cells can also be used to determine and control the compositions of molten salts, as well as to measure the solubilities of various oxidation products in melts [25-28,30]. 

It has been established that salts can deposit or form on metals during gas-metal reactions. Molten layers could then develop at high operating temperatures. Consequently, the laboratory testing of corrosion resistance in molten salts could yield valuable results for evaluating resistance to some high-temperature gaseous environments. 

Electrochemical processes in melts are often attended by side reactions and phenomena complicating the primary process. This is true, in particular, for the technically very important class of reactions in which a number of metals (calcium, barium, and others) are obtained electrometallurgically from molten salts. In many of these processes the metal that is deposited (sometimes in a highly disperse state) is found to interact with the corrosive melt for example, in a reaction such as... 

Electrolyte management, that is, the control over the optimum distribution of molten carbonate electrolyte in the different cell components, is critical for achieving high performance and endurance with MCFCs. Various processes (i.e., consumption by corrosion reactions, potential driven migration, creepage of salt and salt vaporization) occur, all of which contribute to the redistribution of molten carbonate in MCFCs these aspects are discussed by Maru et al. (4) and Kunz (5). 

In fluids that allow conduction of ionic charge, such as solutions of salts in water or molten salts, the corrosion reactions may split into two parts (which may occur in different places) the anodic reaction that results in the conversion of metal to metal cations and produces surplus electrons in the metal, and the cathodic reaction that consumes electrons and hence balances the anodic reaction ... 

Corrosion reactions beneath molten salts are generally complicated, because the number of possible corrosion products is much higher than in the case of gas phase corrosion, and a variety of chemical and electrochemical reactions are possible. 

As the molten salt is electrolytic. Hot Corrosion processes involve electrochemical reactions like oxidation of the metal and reduction of melt components and dissolved gases. Hence, many of investigations of Hot Corrosion have been done by electrochemical techniques, mostly combined with conventional corrosion... 

Gasification may be enhanced by the catalytic properties of the melt used. Molten salts, which are generally less corrosive and have lower melting points than molten metals, can strongly catalyze the steam-coal reaction and lead to very high conversion efficiencies. 

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