Erosion anodized, aluminum

The cells are strong steel boxes, lined with alumina (to act as a refractory), a thermal insulator, and carbon. The cathode is a liquid pool of aluminum that lies at the base of the cell, above a current collector consisting of a number of carbon blocks inlaid with steel bars. A frozen crust of electrolyte protects the cell housing from erosion. The cell has ports for the periodic addition of alumina through the crust, for the removal of A1 metal, and an extractor to vent anode gases (mainly CO2). As the carbon anode is consumed, it is lowered to maintain a constant anode/cathode gap (about 5 cm). In a typical plant for the production of 70,000 tons of A1 per year, 200 Hall-Heroult cells, each 3 m X 8 m in size with 15 m of anode area, are arranged in series. The operating current density is... 

Ship hulls Painting cannot always protect hostile marine conditions, in ships and, areas above keel blocks. Stem and mdder areas suffer erosion and corrosion due to the high turbulence caused by the propeller coupled with the galvanic effects of the noble bronze propeller. Effective cathodic protection of ship hulls and similar marine structures in seawater against corrosion can be apphed using either aluminum or zinc alloy sacrificial anodes. Twenty percent of the anodes required for full hull protection are required for stern protection only. 

To withstand the highly corrosive conditions in aluminum electrolysis cell, the inert anode materials must have excellent oxidation resistance. Among the materials under consideration, Ni-Fe-based alloys and their composite materials have shown a promise for industry application that has received great attention Unfortunately, Ni-Fe alloys under oxidizing conditions develop layered corrosion scales containing Fe O and/or other metal oxides, which may either provide some protection to further oxidation or result in more corrosion/erosion on the alloy anodes during aluminum electrolysis... 

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