Potential scale aluminum alloy

Inhibiting the corrosion of aluminum alloys by adding 1-5% of transition metals is a dramatic case of corrosion protection because of the small amounts of additives that are successful in reducing the corrosion rate by 1-2 orders of magnitude. It turns out that the alloying materials shift the pzc toward the positive side on the potential scale. Thus, in many practical situations, the alloys of the transition metals are in a... 

The oxidation life of ODS FeCrAl alloys is determined by their ability to form or reform a protective alumina scale, and can be related to the time required for the aluminum content of the alloy to be depleted to some minimum level [2-5]. As a result, the service life is a function of the available aluminum content of the alloys and the minimum aluminum level at which breakaway oxidation occurs. Therefore, there is a minimum cross sectional thickness which can be safely employed at temperatures above 1200°C.The major factors that result in depiction of the reservoir of aluminum in the alloy are the inherent growth rate of the aluminum oxide and the tendency for the scale to spall, which results in a (temporary) increase in oxide growth rate in the area affected by spallation. Because of their significantly higher aluminum content >28 at% compared to 9 at%), alloys based on Fe3Al afford a potentially larger reservoir of aluminum to sustain oxidation resistance at higher temperatures and, therefore, offer a possible improvement over the currently-available ODS FeCrAl alloys [61-... 

The molybdenum cleaning process is necessary to remove surface scale, general contamination, and any basis metal that may be present. Among the potential contaminants in wrought products, iron is of primary concern. Others, such as aluminum, carbon, cadmium, copper, and nickel, may also be present as elements, but they are more frequently present in the form of oxides. Removal of a controlled amount of basis metal may be desired to insure complete removal of contaminants. There are three main methods for cleaning molybdenum and molybdenum alloys. 

High-temperature oxidation and corrosion behaviors of Ni-Fe-Cr alloy as inert anodes for aluminum electrolysis have been studied in oxygen and molten electrolyte. The oxidation and corrosion scales on the anodes tested were analyzed using XRD and SEM-EDS. The oxidation rate is found to increase with increasing temperature from 700 °C to 950 °C, which can be approximately described by an inverse power rate function. The oxidation scales at 750 °C, 920 °C and 950 °C contain Cr-rich phase along with FeCr204 and (Eeo.eCro.4)203. The corrosion extent of Ni-Fe-Cr anodes in electrolyte is dominated by temperature, which can make the scales thickness double from 700 °C to 750 °C or from 920 °C to 950 °C. Cr and Fe in the scales on the anode in electrolysis corrode preferentially into the molten electrolyte, while the nickel oxides could better sustain the corrosive environment in electrolysis. The results can be useful for developing inert anode material for potential application in aluminum electrolysis. 

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