Interactions at the border of metal / liquid

Author(s): Essen Suleimenov

The interaction processes at the metal / liquid interface require a more in-depth study to determine the causes of the onset of chemical reactions and determine the most chemically active elements of the metal structure, which lead, in particular, to the onset of pitting corrosion. During cathodic protection, when a constant potential difference is applied, an electric current brings the system into a quasi-equilibrium state. An unsteady electric current can promote or block chemical reactions. The strength of the current flowing through a liquid under conditions of its unsteadiness can vary widely enough due to many physicochemical factors: the presence of a chemical reaction, triboelectric effects, crystallization at the phase boundary, etc. The mechanism of the appearance of electrostatic charges between the surfaces of two moving liquids, a liquid - the solid surface of bodies is still not well understood and requires a fundamental solution to the problem. We studied the influence of electric current parameters on the interaction of iron, aluminum and molybdenum with inorganic aqueous solutions. When iron was leached, a current frequency of 50 Hz, 100 Hz, and 150 Hz was used. The current strength ranged from 100 to 200 mA. The alkali concentration is 1.0 M sodium hydroxide. During the electrochemical dissolution of aluminum electrodes, the reaction began immediately after they were immersed in a KOH solution at a concentration of 3.58% (R = 50 Ohm, h = 50 Hz). An increase in current significantly suppresses the dissolution of aluminum, while an increase in alkali concentration up to 5.7% KOH does not cause a dissolution of aluminum. We have shown that at a current strength of 200–500 mA and a voltage of 1.0–3.2 V with different current frequencies, molybdenum was dissolved in an aqueous solution of potassium oxide at a rate of 0.5–4.3 mg / min. The dissolution rate decreased with increasing current frequency and the reaction completely stopped at 25 ° C and current strength of 90 mA at 66 Hz, for 200 mA - 130 Hz, 270 - 250 Hz, 360 - 350 Hz, 450 - 400 Hz; for 75 ° С and 200 mA at 160 Hz, 300-330 Hz, 500-750 Hz.