Corrosion Electrochemical Behavior of Nickel in the LiCl–KCl Melt Containing Lanthanum Trichloride

Abstract

The effect of temperature on the corrosion of nickel (N1) in the range from 500 to 800°C during testing in the salt melt of the eutectic mixture of lithium and potassium chlorides with the addition of lanthanum trichloride in the amounts from 0.5 to 2 mol % is studied. The nickel corrosion rate increases with temperature, and lanthanum chloride additives decrease the corrosion rate at 500–650°C (inhibition of the shielding type due to the subsequent chemical reaction). The corrosion potential of nickel is approximately –0.5 V relative to the silver chloride electrode at 500°C, insignificantly decreases with temperature, and is independent of the concentration of lanthanum chloride. To specify the mechanism of corrosion damage, current–voltage curves are recorded at lanthanum chloride contents of 0.5 and 2 mol % and sweep speeds of 10 and 20 mV/s. X-ray diffraction analysis and X-ray spectral microanalysis are used. The sweep speed exerts no effect on the irreversible electrochemical oxidation process, and the addition of lanthanum chloride increases the current density in the anodic region tenfold or more. A comparison of the corrosion rates obtained by gravimetric and chemical analytical methods suggests an electrochemical corrosion mechanism.