Yuriy Zaikov

Electrolytic Aluminizing of Low Carbon Steel as Protection Treatment for Current Leads against High Temperature Oxidation

Application of protective aluminum-based coatings is one of the ways to increase the oxidation resistance of low-carbon steel. The electrolytic deposition of aluminum in the NaF33-KF15.2-(AlF3)51.8 wt.% melt at 920°C and the current density of 0.8-1.0 A·cm-2 (0.25 A·h·cm-2) have provided a continuous aluminide coating based on Fe2Al5 with a good adhesion to the steel substrate due to dissolution of oxide film from the surface of the treated products in fluoride melt. The resistance of steel samples to sulfide corrosion was investigated in a lab-scale three-electrode cell at 900°C in contact with a “Soderberg” carbon anode, which was obtained by carbonization of the coal tar pitch containing 2.0-2.5 wt.% of sulphur. The IRC (ohmic voltage drop in contact layer) growth rate was 3.3 times higher for uncoated steel due to formation of the oxide-sulfide layer based on FeS. The electrolytically aluminized steel with preliminarily formed α-Al2O3 layer possessed more stable value of the IRC in comparison with the uncoated steel because of the higher chemical resistance.

Aluminide Coating Application for Protection of Anodic Current-Supplying Pins in Soderberg Electrolytic Сell for Aluminium Production

Anodic current-supplying pins (ACP) made of low-carbon steel corrode intensively due to the sulfur contamination of the carbon-based Soderberg anode and iron sulfides formation in the present aluminium production technology. The aluminide coatings produced by the liquid-phase method followed by the fluoride flux treatment of the steel samples were applied for the ACP protection. The protective layer based on α-Al2O3 and FeAl2O4 was formed on the steel surface in the course of the test run in the industrial Soderberg anode during the aluminium electrolysis. The aluminized ACP wear rates calculated by the linear extrapolation of data obtained during 150 days workout were 4.0 and 5.4 cm/year for the ACP with the aluminide coating and without it, respectively. The current load on the ACP remained almost the same for the aluminized and original uncoated samples with the exception of the initial “heating” period (400-600°C).

Voltammetric and Chronopotentiometric Study of Nonstationary Processes at the Oxygen-Evolving Anodes in KF–NaF–AlF3–Al2O3 Melt

Abstract. Some features of behavior and kinetic of the anodic processes for the platinum and Cu–Fe–Ni alloy in the KF–NaF–AlF3–Al2O3 melts at 1025–1055 K have been studied by cyclic voltammetry and chronopotentiometry.The obtained results allowed us to conclude that mechanisms of the anodic processes at the platinum and Cu–Fe–Ni alloy are similar. Both mechanisms include the oxidation stage of electrode material. A rate of this stage is determined to depend significantly on the melt temperature.