Special high grade zinc

RoUed-zinc products in the form of strip, sheet, wire, and rod have many and varied commercial appUcations. Strip is formed into dry-ceU battery cans, mason jar covers, organ pipes, grommets, eyelets, and many other objects, some of which are subsequentiy brass or chromium plated (jewelry, medaUions, bathroom accessories, etc) (132). The zinc—carbon dry-ceU appUcation accounts for about one half the roUed-zinc consumption in the United States (see Batteries). Sheet zinc is used in photoengraving and also in the constmction of roofing and other architectural uses. Special high grade zinc with a... 

Zn) penny with a less expensive copper-plated penny made from zinc strip (Zn—0.8% Cu alloy) (133,134). Zinc blanks stamped from the Hazelett-cast roUed zinc are barrel-plated with copper prior to coining to produce the finished penny. In 1992, about 22,000 Mt of special high grade zinc were used to make 9.1 biUion pennies. 

Electrolytic Process—in which oxidized zinc concentrates are leached in sulfuric acid and then electrolyzed to plate SHG (special high-grade zinc metal) on the cathode and to regenerate the add on the anode. 

Tin in Special High Grade zinc is held to 0.001% maximum. 

In the indirect process, zinc metal vapor for burning is produced in several ways, one of which involves horizontal retorts. Since the entire vapor is burned in a combustion chamber, the purity of the oxide depends on that of the zinc feed. Oxide of the highest purity requires special high-grade zinc, and less-pure products are made by blending in Prime Western and even scrap zinc. 

The relative distribution of the types of zinc metal product produced and sold is shown in Figure 8. Just under half is Special High Grade Zinc. Eduction of alloys for galvanizing, die casting, and other casting totals 23%. Figure 9 shows the distribution of cast zinc shapes and sizes. A little more than half of the production is in the form of 25-kg slabs. 

Most of the world s zinc production is obtained via the roast/leach/electrowinning (RLE) process. Starting from sulphidic concentrates, this hydrometallurgical process allows the production of special high-grade zinc. During this process, an iron rich residue (goethite or jarosite) is produced. This residue has to be stockpiled, and this is clearly an environmental issue for the future. 

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