OXIDATION KINETIC AND ANODIC BEHAVIOR OF Zn22Al ALLOY DOPED WITH NICKEL

The article presents the results of the study of the oxidation kinetics and the anodic behavior of the zinc-aluminum alloy Zn22Al, doped with nickel, in various corrosive environments. The kinetic and energy parameters of the process of high-temperature oxidation of alloys are determined. It is shown that the process of high-temperature oxidation of samples of Zn22Al-Ni alloys is characterized by a monotonic decrease in the true oxidation rate and an increase in the effective activation energy at the content of the alloying component in the initial Zn0.5Al alloy up to 0.5 wt.%. It was found that nickel additives within the studied concentration (0.01-0.5 wt.% ) slightly increases the oxidability of the base alloy Zn22Al at temperatures of 523, 573 and 623 K. It is shown that the dependence of the corrosion potential of zinc-aluminum alloys on the nickel content in them is of the same type, i.e. the additives of the alloying component contribute to the displacement of the corrosion potential in the region of positive values. The influence of the aggressiveness of the corrosive medium on the anodic behavior of alloys when comparing concentrated electrolytes with the increasing concentration of chloride ions in the sodium chloride solution is established. It is determined that the potentials of pitting formation and repassivation of the initial alloys shift to a more positive region with an increase in the nickel concentration in the alloys. The greatest shift of these potentials to the positive region is observed when alloying alloys containing small nickel additives. It is shown that the corrosion products of the studied alloys consist of a mixture of protective oxide films Al2O3, ZnO, NiO, Al2O3·ZnO and Al2O3·Ni2O3. It was found that the alloying of zinc-aluminum alloys with nickel (in the range of 0.01–0.05 wt.%) reduces the corrosion rate of the base alloy by 2-3 times. The proposed alloy compositions can be used as an anode coating for corrosion protection of steel products and structures.

Contribution of modulated mass transport by magnetic field to the anodic behavior of iron with various electrode configurations

Effects of horizontal magnetic field paralleling to the iron electrodes with various configurations on the anodic behavior in sulfuric acid solution are investigated. The magnetic field effect is stronger for the horizontally placed upward electrode than for the horizontally placed downward and the vertically placed electrodes. Locally dissolution-mitigated regions are found at two ends of the electrode along the direction perpendicular to the magnetic field direction in addition to the locally accelerated dissolution region at two ends paralleling to the magnetic field direction. The effect of magnetic field on convection process is critical in determining the anodic current density.

EFFECT OF CALCIUM ON THE ANODIC BEHAVIOR OF ALUMINUM CONDUCTOR ALLOY AlTi0.1 IN THE MEDIUM OF THE ELECTROLYTE NaCl

The article presents the results of an experimental study of the effect of calcium on the anodic behavior of the aluminum alloy AlTi0.1, in the medium of NaCl electrolyte. The study was carried out by the potentiostatic method in the potentiodynamic mode at the potential sweep rate of 2 mV / s. It is shown that the modification of the aluminum alloy AlTi0.1 with calcium promotes the displacement of the potentials of free corrosion, pitting formation, and repassivation to the positive range of values. The corrosion rate of the aluminum alloy AlTi0.1 when modified with 0.01-0.5 wt % calcium decreases by 10-17 %.

Passivation of chromium disilicide in acidic media

The anodic behavior of CrSi2 electrode in 0,5 M H2SO4, 0,5 M HClO4, 0,5 M HNO3 and 0,5 M HCl solutions has been studied by the methods of polarization, capacitance, and impedance measurements. It has been concluded that in the process of anodic oxidation at potentials from corrosion E to transpassivation E inclusive, an oxide film is formed on the surface of chromium disilicide in the studied media, which is close in composition to SiO2 (with a small content of chromium oxides). The presence of this film on the silicide surface determines its high chemical resistance in the studied solutions. The thickness of the oxide film on CrSi2 has been calculated depending on the potential and composition of the electrolyte. The growth constant of the oxide film has been determined.