Lead alloys composition

The classical large-scale method for preparation of tetraethyllead and tetramethyllead is by reaction of alkyl halide with sodium/lead alloy (composition Pb Na 1/1 )38. The product is isolated by steam distillation and yields are high ... 

Ho CT, Carbon-fiber-reinforced tin-lead alloy composites, J Mater Res, 9(8), 2144-2147, 1994. 

Only lead alloys containing copper below 0.08% have practical appHcations. Lead sheet, pipe, cable sheathing, wine, and fabricated products are produced from lead—copper alloys having copper contents near the eutectic composition. Lead—copper alloys in the range 0.03—0.08 wt % copper are covered by many specifications ASTM B29-92 (7), QQL 171 (United States), BS 334, HP2 Type 11 (Canada), DIN 1719 (Germany), and AS 1812 (Austraha). 

Antimony Alloys. Approximately one-half of the total antimony demand is for metal used in antimony alloys. Antimonial lead is a term used to describe lead alloys containing antimony in proportions of up to 25%. Most commercial lead—antimony alloys have antimony contents less than 11%. The compositions of several important antimony alloys are given in Table 4. 

The compositions of the phases can change provided that their relative proportions change so as to lead to the same overall alloy composition. In practice changes in phase composition occur by diffusion. 

From 245°C to 183°C. The liquidus is reached at 245°C, and solid (a lead-rich solid solution) first appears. The composition of the liquid moves along the liquidus line, that of the solid along the solidus line. This regime ends when the temperature reaches 183°C. Note that the alloy composition in weight % (64) is roughly half way between that of the solid (81 wt%) and liquid (38 wt%) so the alloy is about half liquid, half solid, by weight. 

Finally it must be remembered with these anodes that Pb02 film, which acts to provide the current leakage, can be detached even when no current is flowing. With renewed anodic loading, the film has to be reformed, which leads to a corresponding consumption of anode material. The anodes should therefore be operated as continuously as possible with a basic load. An exhaustive treatment of the composition and behavior of lead alloy anodes can be found in Ref. 13. 

Besides Type A lead, nine lead alloys are specified in British Standards for various purposes. Their compositions and impurity limits are given in Table 4.13. In addition, alloys for batteries and for anodes are of importance. In due course it is likely that European standards will supersede the current national ones... 

BS 1 1984 Composition of lead and lead alloy sheaths for electri< cahtes... 

There may also be a need to consider the performance of pre-corroded test specimens. Apart from the fact that these conditions frequently arise in service it is also important for two other reasons. First, the presence of corrosion products or other surface layers may affect the access of constituents of the environment to the underlying metal surface-where the corrosion process occurs —and, second, in the case of alloys some pre-corrosion may lead to compositional changes in the surface. These factors should be taken into account in the application of any test method. 

Consequently, ions such as BF4 and PFf), which might be expected to complex or solvate an electroactive metal species, are not expected to be reduced and to influence alloy composition, unlike AICI4 and A ECU. In principle, this should lead to better control of alloy composition since the concentrations of the electroactive species may be controlled independently. For example, one can avoid an electroactive species such as [Ti(AlCl4)3] which is likely responsible for the limited composition range found in Ti-Al alloys electrodeposited from chloroaluminates. 

Therefore, passivation of the positive electrode by poorly conducting PbS04 can be reduced [348]. The porosity is important because it enables the expansion during the solid phase volume increase, which accompanies the transformation of Pb02 to PbS04. In the most popular construction, the electrode paste material (mixture of metallic lead with lead oxides) is held in a framework composed of lead alloys with additions of tin, antimony, selenium, and calcium [348]. Antimony improves the mechanical stability however, it increases the resistance and facilitates the selfdischarge of the battery. Better results are obtained for low antimony content and/or for lead-calcium alloys [203]. Methods of positive electrodes improvement, from the point of view of lead oxide technology have been discussed [350]. Influence of different factors on life cycle, nature, and composition of the positive active mass has been studied by Pavlov with coworkers [200, 351, 352]. 

The transient behavior at the interface of two ternary alloy compositions in a system with complete solid solubility will lead to a path in composition space as shown in Fig. 6.1. Evolution is initially parallel to the fast eigendirection / and, after its gradients become small, finally proceeds parallel to the slow direction s. 

This method, based pir fiie variability of the specific gravity of tin-lead alloys according to hefr composition, is rapid and gives approximately the proportion of thread. 

The term babbitt includes high tin alloys (substantially lead-free) containing >80 wt % tin, and high lead alloys containing >70 wt % lead and <12 wt % tin. Both have the characteristic structure of hard compounds in a soft matrix, and although they contain the same or similar types of compounds, they differ in composition and properties of the matrix. 

Alloys are prepared commercially and in the laboratory by melting the active metal and aluminum in a crucible and quenching the resultant melt which is then crushed and screened to the particle size range required for a particular application. The alloy composition is very important as different phases leach quite differently leading to markedly different porosities and crystallite sizes of the active metal. Mondolfo [14] provides an excellent compilation of the binary and ternary phase diagrams for aluminum alloys including those used for the preparation of skeletal metal catalysts. Alloys of a number of compositions are available commercially for activation in the laboratory or plant. They include alloys of aluminum with nickel, copper, cobalt, chromium-nickel, molybdenum-nickel, cobalt-nickel, and iron-nickel. 

---