Lead-based alloys

In determining the purity or percentage of lead in lead and lead-base alloys, the impurities or minor components are deterrnined and the lead content calculated by difference. Quality control in lead production requires that the concentration of impurities meet standard ASTM specifications B29 (see Table 7). Analyses of the individual impurities are performed using various wet chemical procedures and instmmental methods such as emission spectroscopy. 

There are obviously situations which demand considerable over-design of a cathodic protection system, in particular where regular and efficient maintenance of anodes is not practical, or where temporary failure of the system could cause costly damage to plant or product. Furthermore, contamination of potable waters by chromium-containing or lead-based alloy anodes must lead to the choice of the more expensive, but more inert, precious metal-coated anodes. The choice of material is then not unusual in being one of economics coupled with practicability. 

Aluminum is not embrittled by low temperatures and is not subject to external corrosion when exposed to normal atmospheres. At 200°C (400°F) its strength is less than half that at room temperature. It is attacked by alkahes, by traces of copper, nickel, mercury, and other heavy-metal ions, and by prolonged contact with wet insulation. It suffers from galvanic corrosion when coupled to copper, nickel, or lead-base alloys but not when coupled to galvanized iron. 

The lead-base babbitts are based upon the lead—antimony—tin system, and, like the tin-base, have a structure of hard crystals in a relatively soft matrix. The lead-base alloys are, however, more prone to segregation, have a lower thermal conductivity than the tin-base babbitts, and are employed generally as an inexpensive substitute for the tin-base alloys. Properly lined, however, they function satisfactorily as bearings under moderate conditions of load and speed. 

A major problem in the analysis of lead-based alloys is the selection of a suitable solvent mixture. Price [7] has described a method based on hydro-bromic acid/bromine. The disadvantage of this method is that the solvent mixture is unpleasant to handle and precipitation often occurs on dilution. Hwang [8] has described a method for the analysis of trace and minor elements in lead/tin solders using a solvent mixture of fluoboric acid and nitric acid. 

INSTRUMENTAL PARAMETERS FOR THE ANALYSIS OF LEAD-BASED ALLOYS... 

Instrumental parameters for the analysis of lead-based alloys are shown in Table 7 and results obtained by Hwang [8] for the analysis of impurities in lead solder are shown in Table 8. 

The problem facing all smelters is that there is a continuous occurrence of antimony in their lead streams, at a time when there is a rapidly declining demand for the element. Declining sales of the alloy, which coincide with increasing use of soft-lead-based alloys, will result in antimony effectively becoming a major contaminant that requires removal. Whilst it is relatively easy for secondary reflners to remove antimony from the bullion, the antimony-rich residue from the process may have to be stockpiled. The residue, which contains around 80 to 90wt.% lead, effectively ties up lead units and can have a major cost impact on the reflnery. 

Considerable experience has been gained in the Russian Federation with lead-bismuth (PbBi) eutectic alloy application as reactor coolant. Since Bi is sufficiently rare and expensive metal, and also it is a source of volatile a-active Vo, the proposal to use lead as a coolant in power fast reactors is now under consideration in several countries. Lead based alloys are currently being considered for hybrid systems (accelerator driven fast reactors) in which the coolant could double as the spallation source for driving the core. 

C. L. Luke "Photometric Determination of Tin in Copper-Base and Lead-Base Alloys" Anal. Chem. 31, 1803-04 (1959). 

Rao, P, Calcium Tin Silver Lead Based Alloys and Battery Grids and Lead Acid Batteries, U.S. Patent 5,298,350 (March 29,1994). 

Characteristics of solder defects, and micro-structural and failure features of tin-based lead-free solder alloys, are somewhat different from tin-lead-based alloys. The difference is apparent when nondestructive techniques such as optical... 

In collaboration with Multicore Solders, Nokia developed a lead-free solder alloy suitable for use in mobile telephones. The alternative Sn-3.8Ag-0.7Cu alloy utilizes existing manufacturing processes to replace lead-based alloys in the assembly of surface-mount PCBs. In production trials, 20 Nokia 2110 GSM digital cellular handsets were assembled using the lead-free solder. The alternative alloy was found to exhibit better solderability than the traditional Sn-Pb solder. 

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