True Brass sinks or protect bench tops where a large amount of acid is used. Lead-lined pipes are used in systems that carry This  is  an  alloy  of  copper  and  zinc.  Additional corrosive chemicals. Frequently, lead is used in alloyed elements, such as aluminum, lead, tin, iron, manganese, form  to  increase  its  low-tensile  strength.  Alloyed  with or  phosphorus,  are  added  to  give  the  alloy  specific tin,  lead  produces  a  soft  solder.  When  added  to  metal properties.  Naval  rolled  brass  (Tobin  bronze)  contains alloys,  lead  improves  their  machinability. about 60% copper, 39% zinc, and 0.75% tin. This brass is highly corrosion-resistant and is practically impurity free. CAUTION Brass sheets and strips are available in several grades: soft, 1/4 hard, 1/2 hard, full hard, and spring When working with lead, you must take grades. Hardness is created by the process of cold roll- proper precautions because the dust, fumes, or ing. All grades of brass can be softened by annealing at vapors from it are highly poisonous. a temperature of 550°F to 600°F then allowing it to cool by  itself  without  quenching.  Overheating  can  destroy the zinc in the alloy. Zinc Bronze Bronze is a combination of 84% copper and 16% tin and  was  the  best  metal  available  before  steel-making techniques  were  developed.  Many  complex  bronze  al- loys, containing such elements as zinc, lead, iron, alu- minum, silicon, and phosphorus, are now available. Today, the name bronze is applied to any copper-based alloy that looks like bronze. In many cases, there is no real distinction between the composition of bronze and that of brass. Copper-Nickel  Alloys Nickel is used in these alloys to make them strong, tough, and resistant to wear and corrosion. Because of their high resistance to corrosion, copper nickel alloys, containing  70%  copper  and  30%  nickel  or  90%  copper and 10% nickel, are used for saltwater piping systems. Small  storage  tanks  and  hot-water  reservoirs  are  con- You often see zinc used on iron or steel in the form of  a  protective  coating  called  galvanizing.  Zinc  is  also used in soldering fluxes, die castings, and as an alloy in making brass and bronze. Tin Tin has many important uses as an alloy. It can be alloyed with lead to produce softer solders and with copper to produce bronze. Tin-based alloys have a high resistance to corrosion, low-fatigue strength, and a com- pressive  strength  that  accommodates  light  or  medium loads. Tin, like lead, has a good resistance to corrosion and  has  the  added  advantage  of  not  being  poisonous; however, when subjected to extremely low tempera- tures, it has a tendency to decompose. Aluminum strutted of a copper-nickel alloy that is available in sheet This metal is easy to work with and has a good form.  Copper-nickel  alloys  should  be  joined  by  metal- appearance. Aluminum is light in weight and has a high arc welding or by brazing. strength per unit weight. A disadvantage is that the Lead tensile strength is only one third of that of iron and one fifth of that of annealed mild steel. A heavy metal that weighs about 710 pounds per cubic foot. In spite of its weight, lead is soft and malle- able and is available in pig and sheet form. In sheet form, it is rolled upon a rod so the user can unroll it and cut off the desired amount. The surface of lead is grayish in color; however, after scratching or scraping it, you can see that the actual color of the metal is white. Because it is soft, lead is used as backing material when punching holes with a hollow punch or when forming shapes by hammering copper sheets. Sheet lead is also used to line Aluminum alloys usually contain at least 90% alu- minum. The addition of silicon, magnesium, copper, nickel, or manganese can raise the strength of the alloy to that of mild steel. Aluminum, in its pure state, is soft and has a strong affinity for gases. The use of alloying elements is used to overcome these disadvantages; how- ever, the alloys, unlike the pure aluminum, corrodes unless  given  a  protective  coating.  Threaded  parts  made of  aluminum  alloy  should  be  coated  with  an  antiseize compound to prevent sticking caused by corrosion. 1-7