Lead coat

Because of the ease with which they can be soldered, electroplated tin—lead coatings of near eutectic composition (62 wt % tin) are extensively used in the electronics industry for coating printed circuit boards and electrical coimectors, lead wires, capacitor and condenser cases, and chassis. 

A ternary tin—copper—lead coating, 2 Cu—8 Sn—90 Pb, is a standard overplate for steel-backed copper—lead automotive bearings. 

Application. Pairs of pipes have been buried in 11 different locations to determine corrosion on nonbitiiminoiis pipe coatings for underground use. One type includes a lead-coated steel pipe and the other a bare steel pipe. 

Soil type Lead-coated steel pipe Bare steel pipe d = difference... 

Since the sample t of—2.86 < tabled t of—2.228, reject Hq and accept Hy, that is, it has been demonstrated that, on the basis of the evidence, lead-coated steel pipe has a greater corrosion resistance than bare steel pipe. 

Lead coatings are mainly applied by cladding and find principal use in the chemical industry for resistance to sulphuric acid, for cable sheathing resistant to attack by soils and in architectural applications where resistance to industrial atmospheres is particularly good. They rely for their protective action on the formation of insoluble corrosion products which stifle the corrosion reaction and lead to very long service lives, but the corrosion resistance is impaired when chlorides are present. 

There is thought to be an explosive form of arsenic, possibly including a combination of unknown structure. This fomri is obtained when sulphuric acid, which is strongly charged with arsenic, is in contact with an iron container protected by a lead coating. It detonates on friction or impact. An analysis attempt did not indicate the presence of hydrogen. This case is similar to that of antimony. 

Cars with catalytic converters use lead-free petrol in order to prevent a lead coating forming on the surface of the catalyst. 

Before 1970 there was very little unleaded gasoline on the market, but by 1974 all gas stations were offering it. In 1974, unleaded fuel had become a necessity for most new cars because of their catalytic converters placed in the exhaust system. These contain platinum or palladium compounds that act as a surface catalyst to bum the hydrocarbons more completely. But lead coats the platinum and palladium and deactivates the converters, so unleaded gas must be used. Up to 4 g/gal of lead could be used in the 1970s, but this was decreased to 0.1 g by 1986. Since 1995 no leaded gas could be used in the U.S. Fig. 7.6 shows the dramatic shift from leaded to unleaded gas between 1975 and 1992. 

Iodine is packed and supplied in polyethylene-lined fiber drums or high sihcon iron, Hastelloy B, or lead coated steel containers. Glass, graphite and acid-proof bricks are very suitable for storing iodine and its solutions. 

On my sulfuric acid production unit in Texas City, we had an electrostatic precipitator to remove a liquid sulfuric acid mist from a flowing gas stream. It worked in the same way as a precipitator in liquid-liquid service. However, the electrodes or grids were not parallel plates. As illustrated in Fig. 26.4, the grids were lead tubes and lead-coated wires. 

This electric sulfuric acid-mist precipitator worked fine, until one of the lead coated wires inside the tubes broke. Then the entire precipitator would arc. This means, the amps would jump up and down, as the single broken wire flapped around inside the tube. I do not know why, but the wires failed only on weekends. Then your fearless author would crawl inside the precipitator, and cut out the broken wire and plug the tube with a wooden plug. 

Alkylation reactions employing alkyl halides are carried out in an acidic medium. For example, hydrobromic acid is formed when methyl bromide is used in the alkylation leading, and for such reactions an autoclave with a replaceable enameled liner and a lead-coated cover is suitable. 

Detectable FDR is mostly particulate in nature. Unjacketed lead bullets produce residue in which greater than 70% of the particles are lead. Coated bullets give the same result, except that a substantial proportion of the lead particles contain copper from the coating material. With jacketed or semi-jacketed bullets the proportion of lead particles in the residue is greatly reduced. It was concluded that most of the lead in the residue comes from the bullet rather than from the primer. This has subsequently been confirmed by experiments involving the use of radioactive tracers.172... 

Tin—lead coatings (10—60 wt % tin) can be applied by hot-dipping or electrode position to steel and copper fabricated articles and sheet. A special product is teme plate used for roofing and flashings, automobile fuel tanks and fittings, air filters, mufflers, and general uses such as covers, lids, drawers, cabinets, consoles for instruments, and for radio and television equipment. Teme plate is low carbon steel, coated by a hot-dip process with an alloy of tin and lead, commonly about 7—25 wt % tin, remainder lead. Electroplating is another possibility. 

In general Cu is added to lead in amounts of up to 0.08% Alloys with addition of Ba, Ca, Co, Au, Li, Mg, Ni, Pt, Na, Ti and Zn have been tested for corrosion resistance anodes made of Ni and Ti give good performance in sulfuric acid solutions Ni in lead improves the weldability of steel during lead coating... 

When the box is used for productions of radiopharmaceuticals incorporating a-or P-emitting radionuclides, closed box units without any lead coating may be sufficient. When handling radionuclides with mixed emitting properties, a possibility is to concentrate the shielding to critical parts of the process. This can be done by use of local shielding inside the production unit. However, for aseptic production, one must keep in mind a potential disturbance of the airflow inside the box. 

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