V. B. Malkov

Magnesium alloys spontaneous dissolution features under external anodic polarization in presence of inhibitors

The effect of benzotriazole (BTA) and sodium ethylenediamine tetraacetate (EDTA) to the magnesium dissolution intensity under external anodic polarization was studied. The inhibiting properties of BTA and EDTA in electrochemical corrosion of magnesium were found in the concentration range from 0.005 to 0.0125 M in sodium sulfate solution and from 0.0025 to 0.03 M in sodium chloride solution. In the presence of inhibitors, magnesium dissolution becomes uniform with decreasing surface hydrogenation and crumbling intensity of small particles into solution.

Creation of Thin Oxide Coatings and Oxide Nanopowders by Anodic Oxidation of Metals in Molten Salts

We studied the feasibility of synthesizing ultrafine oxide powders by anodic oxidation of metals, such as zirconium and tantalum, in chloride + nitrate melts at temperatures above 830K. We showed that, varying the electrolyte composition, oxidation temperature, and anodic current density, one obtains either compact protective coatings on the specified metals or oxide powders with particle sizes of 50 to 200 nm.

High-temperature electrochemical synthesis of oxide thin films and nanopowders of some metal oxides

An electrochemical method is proposed for preparing metal (aluminum, titanium, tantalum, zirconium) oxides with a high affinity to oxygen in a chloride-nitrate melt at temperatures above 830 K in an argon atmosphere. It is demonstrated that either dense metal oxide layers firmly bonded to the metal base can be produced or large amounts of nanosized oxides can be formed in the melt bulk depending on the anodic oxidation conditions (electrolyte composition, oxidation temperature).

Effect of plasma treatment on corrosion-electrochemical interaction between titanium and chloride-nitrate melt

The corrosion-electrochemical behavior of titanium in a chloride melt containing 1–30 wt % sodium nitrate at a temperature of 790–900 K in an argon atmosphere is studied. Depending on the sodium nitrate content, either oxide layers of various structures can appear on the titanium surface or titanium dioxide nanopowder can form in the bulk of the melt. Treating VT-1 titanium with hydrogen or helium high-temperature pulsed plasma substantially changes the morphology and protective properties of the oxide films produced on titanium.

Corrosion and anodic dissolution of magnesium alloys in the presence of inhibitor

The effect of NTPS inhibitor on the corrosion behavior of magnesium alloys with various contents of alloying components is studied. NTPS is found to be an effective corrosion inhibitor in the absence of energizing, but under the anodic polarization, it does not produce any noticeable effect on the self-dissolution process. Comparative analysis of the processes proceeding at the anodic dissolution of magnesium and electron-microscopic studies of the specimens showed that the dissolution is accelerated due to the active-surface development. A supposition that, under the effect of a constant anodic current, the development and formation of the magnesium surface relief takes place at the initial polarization stage is put forward.

The mechanism of formation of thin oxide coatings and nanopowders at the anodic oxidation of zirconium in molten salts

At the oxidation of zirconium in molten salts up to 813–1073 K, the growth of oxide phases is found to proceed chiefly due to the diffusion of oxygen ions via the oxide film toward the metal-oxide interface. An oxide film formed in the initial period of zirconium oxidation in a chloride-nitrate melt decelerates the process but does not prevent the ion exchange at the metal-melt boundary. As the oxide formation proceeds and the steady-state conditions of the corrosion process are reached, the oxidation rate becomes limited by the diffusion of oxygen ions from the film surface deep into the metal. Along with the diffusion of O2− ions at temperatures of 813 to 1073 K, zirconium ions can also migrate in the metal, which makes interpreting the whole process much more difficult. At the oxidation, the films of various colors (from black to light gray) with diverse corrosion and protective properties, as well as fine-dispersed powder of zirconium dioxide with a mean size of particles up to 30 nm, are formed.

Selective Dissolution of Brass in the Molten Eutectic Mixture of Lithium, Sodium, and Potassium Carbonates

The dissolution of L63 brass in molten alkali metal carbonates is shown to occur at an operating temperature of 773 K in the potentiostatic and galvanostatic regimes. The size and number of pores are found to depend on the electrochemical parameters, namely, the applied potential and the current density.

Formation of titanium diboride coatings during the anodic polarization of titanium in a chloride melt with a low boron oxide content

The corrosion-electrochemical behavior of titanium in a molten eutectic mixture of cesium and sodium chlorides containing up to 1 wt % boron oxide is studied in the temperature range 810–870 K in an argon atmosphere. The potential, the current, and the rate of titanium corrosion are determined. The optimum conditions of forming a dense continuous titanium diboride coating on titanium with high adhesion to the metallic base are found for the anodic activation of titanium in the molten electrolyte under study.

Corrosion-electrochemical properties of the anodic oxide films formed on aluminum in a chloride-nitrate melt in a 0.5 M Aqueous NaCl solution

The corrosion-electrochemical behavior of aluminum is studied in a chloride-nitrate melt containing 50 wt % eutectic mixture of cesium and sodium chlorides and 50 wt % sodium nitrate in the temperature range 790–900 K in an argon atmosphere.

Corrosion-electrochemical behavior of nickel in an alkali metal carbonate melt under a chlorine-containing atmosphere

The corrosion-electrochemical behavior of a nickel electrode is studied in the melt of lithium, sodium, and potassium (40: 30: 30 mol %) carbonates in the temperature range 500–600°C under an oxidizing atmosphere CO2 + 0.5O2 (2: 1), which is partly replaced by gaseous chlorine (30, 50, 70%) in some experiments. In other experiments, up to 5 wt % chloride of sodium peroxide is introduced in a salt melt. A change in the gas-phase composition is shown to affect the mechanism of nickel corrosion.