Aluminum alloying element

Some of the common aluminum alloying elements and their imparted properties are outlined in TABLE 9-6. 

TABLE 9-6. Common Aluminum Alloying Elements and Their Properties... 

Copper is primarily alloyed to increase strength, however, electrical and thermal conductivities, corrosion resistance, formabiUty, and color are also strongly affected by alloying. Elements typically added to copper are 2inc, tin, nickel, iron, aluminum, siUcon, chromium, and beryUium. 

The anodes are generally not of pure metals but of alloys. Certain alloying elements serve to give a fine-grained structure, leading to a relatively uniform metal loss from the surface. Others serve to reduce the self-corrosion and raise the current yield. Finally, alloying elements can prevent or reduce the tendency to surface film formation or passivation. Such activating additions are necessary with aluminum. 

Pure aluminum cannot be used as an anode material on account of its easy passivatability. For galvanic anodes, aluminum alloys are employed that contain activating alloying elements that hinder or prevent the formation of surface films. These are usually up to 8% Zn and/or 5% Mg. In addition, metals such as Cd, Ga, In, Hg and T1 are added as so-called lattice expanders, these maintain the longterm activity of the anode. Activation naturally also encourages self-corrosion of the anode. In order to optimize the current yield, so-called lattice contractors are added that include Mn, Si and Ti. 

Because it is difficult to remove alloying elements such as copper and zinc from an aluminum melt, separate collection and separate reutilization of different grades of aluminum scrap are necessary. Note that secondary aluminum... 

Most commercial uses of aluminum require special properties that the pure metal cannot provide. The addition of alloying elements imparts strength, improves formability characteristics, and influences corrosion resistance properties. The general effect of several alloying elements on the corrosion behavior of aluminum has been reported by Godard et al. (2) as follows ... 

Copper reduces the corrosion resistance of aluminum more than any other alloying element. It leads to a higher rate of general corrosion, a greater incidence of pitting, and, when added in small amounts (for example, 0.15% ), a lower rate of pitting penetration. 

Alloying element with CVD aluminum to reduce electromigration. 

Aluminum is not commonly used as an alloying element in steel to improve oxidation resistance, as the amount required interferes with... 

A consideration of the electrochemical behavior of the large variety of aluminum alloys used in practice surpasses by far the scope of this chapter. Nevertheless, we consider it useful to review here the effect of some elements that have a profound effect on this behavior. 

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