The possibility of using alkaline-stannate electrolytes in hydronic chemical current source as the hydrogen generator
Aircraft engines and power generators
Аuthors*, **, ***, ****, *****, ******
Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
The article presents the investigations results of the most effective electrolyte-cathode compositions searching for hydronic chemical current source (CCS) with an aluminum anode. We examined current-voltage characteristics (CVC) of some metals and alloys — nickel, molybdenum, titanium, and steel Ст3 in purely alkaline electrolyte (4 M NaOH), and in alkaline electrolyte with addition of sodium stannate: 4M NaOH + 0,06M Na2SnO3∙3H2O. This alkali-stannate electrolyte has been sel ected for research because it is the most effective in terms of alkali aluminum anode corrosion inhibition in air-aluminum (AA) CCS with a gas diffusion cathode (GDC).
The best CVC in pure alkaline solution were obtained for molybdenum and nickel. However, molybdenum as the cathode showed a high tendency to hydrogen embrittlement. After a series of cathode tests the electrode made of molybdenum foil (0.1 mm) collapsed when installed in the test cell due to the small deforming effects.
In the alkaline-stannate electrolyte CVC of cathodes made of different metals were significantly deteriorateв due to the formation of the tin coating on the surface to a different degree, especially in prolonged and/or repeated use.
To explain the causes of different degree of potential reduction we carried out the structure investigations of the formed coating in the alkali-stannate electrolyte of electrodes made of various metals. The investigations were made by X-ray diffraction and scanning electron microscopy (SEM). The surface of nickel electrode was studied. The electrode was tested as the cathode for three experiments in a row to obtain discharge characteristics of a hydronic CCS in a cell with an anode fr om an Al-In alloy. Stationary discharge current was set to 1000 A/m2.
As the experiments showed, the structure of the tin coating formed on the electrode surface is porous with a high degree of porosity (~ 50%). It causes the difference in the CVCs of cathodes of different metals due to hydrogen evolution, both on the surface of the substrate (base material), and on surface coating.
Thus, it is shown that the use of stannate ions additives to the alkaline electrolyte of a hydronic CCS is undesirable, since it leads to deterioration of cathodes’ characteristics. Therefore, for inhibiting of the aluminum anode corrosion and, thereby, for increasing its use factor, it is necessary to introduce additions of organic inhibitors in an alkaline electrolyte of a hydronic CCS.
Keywords:chemical current source, power plant, hydrogen generator, corrosion inhibitor, corrosion characteristics
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