Electrochemical Behavior of ATsKM Sacrificial Anodes in the Course of Long-Term Operation on Seagoing Ships

We studied the electrochemical properties of a sacrificial-anode alloy based on aluminum and magnesium, into which calcium, along with zinc, was introduced as an antipassivator. For the production of this alloy, we used waste and scrap of aluminum-magnesium alloys. In addition to iron and silicon admixtures, it contains a significant amount of copper. Aluminum-based solid solution is the main phase of the new sacrificial-anode alloy, and its second phase represents Ca_x Zn_y Al_z intermetallic compound, which is distributed uniformly over the volume. The proposed alloy was used for the corrosion protection of seagoing ships of the Baltic Steamship Line. It was also tested successfully in waters of the Pacific and in corrosive brackish soils of Southern Ukraine and Middle Asia. These sacrificial anodes have an efficiency of ∼85% and a stationary potential in seawater of −1.10 v relative to a copper-sulfate reference electrode.__________Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 5, pp. 95–98, September–October, 2004.     

Electrolytic Corrosion of Titanium Carbonitride Composites

The corrosion properties of TiCN, TiCN – AlN, and (TiCN – AlN) – (Fe – Cr) ceramics as well as those of the individual components TiN and TiC in a 3% NaCl solution have been investigated. The kinetics and the mechanism of anode dissolution of metals and oxidation of specimens have been studied by using polarization curves, chemical and x-ray phase analyses, Auger electron spectroscopy, and scanning electron microscopy (SEM). TiCN and TiCN – AlN composites have been found to be the most corrosion-resistant. The presence of a metallic binder in the titanium carbon nitride somewhat decreases the corrosion resistance of the ceramics. On the whole, however, the ceramics developed boast a significantly higher corrosion resistance than that of structural steel.     

Electrolytic corrosion of materials of TiCrB<Subscript>2</Subscript>–AlN system in 3% NaCl solution

The corrosion resistance of titanium-chromium-diboride-based ceramic materials and cermets in 3% NaCl solution (to simulate sea water) is studied by the method of potentiodynamic polarization curves. The composition and microstructure of oxidized specimen surfaces are examined. Adding small amounts of AlN (5 to 10 vol %) to TiCrB₂ provides an essential improvement of the corrosion resistance. Introduction of an NiAlCr metallic binder into the material composition results in a lower resistance to anodic oxidation.     

Formation of oxide films on the surface of tungsten disilicide during anodic oxidation

Oxide-layer formation on the surface of tungsten disilicide is studied during its electrochemical polarization in a 3% NaCl solution at 20 °C. It is indicated that the total thickness of the oxide layer that forms over a period of 90 min does not exceed 10 nm. The following multistage mechanism of anodic oxidation is established: tungsten oxides (for example, W₃O and W_O3) in which the greater the polarization, the greater the extent to which the metal is oxidized, the lower tungsten silicide W₅Si₃, and silica are formed. It is demonstrated that a double electrolytic layer on the interphase boundary between the tungsten disilicide and 3% NaCl solution is formed owing to dissociation of the silanolic groups situated a priori on the surface of the silicide. Here, the surface of the electrode acquires a negative charge, while the positively charged diffusion layer contains hydroxone ions. As a silica film forms on the WSi₂, the material becomes more corrosion-resistant. On the whole, the scheme established for electrochemical oxidation of WSi₂ complies with the mechanism of its high-temperature oxidation.     

Electrochemical Behavior of AlB12–AlN Composites in Natural Environments

Powder Metallurgy and Metal Ceramics - Electrochemical processes occurring on ceramic AlB12–AlN composites induced by polarization in a 3% NaCl aqueous solution at 37°C are examined for...