September/October 1992
Antimony, bismuth, and cadmium fill narrow but vital niches in a variety of industries.
BY JEFF BORSECNIK
Jeff Borsecnik is assistant editor of Scrap Processing and Recycling.
Often called minor metals, the specialty metals are a mixed lot, with diverse characteristics and applications. They don't even have a clear-cut definition, though many say it's metals with less than 25,000 tons of annual production. All are produced in smaller volumes than the major metals, and they are usually byproducts of base metals. As such, the minor metals are often characterized by inflexible supply and price volatility.
Here's an introduction to three of those that might be casually considered major minor metals: antimony, bismuth, and cadmium.
A Is for Antimony
The name "antimony" is derived from the Greek words "anti" and "monos," which together render "a metal seldom found alone," notes Thomas O. Llewellyn, a physical scientist with the U.S. Bureau of Mines (Washington, D.C.). Not only is antimony generally found and produced with other metals, but its uses—whether as an alloy or oxide—team it with partners.
Antimony has long been used as a hardening agent in the lead grids of storage batteries, but this market has decreased in recent years. In the shift toward maintenance-free batteries, manufacturers have put calcium in place of much of the antimony previously used (high-antimony batteries need to be regularly refilled with water.). Other materials also compete in some applications with antimony, which faces the disadvantageous label of "suspected carcinogen." Flame-retardant compounds, however, which pair the element with a bromine or chlorine compound, promise growing demand for antimony. In fact, the metal's primary niche today is in flame-retardant compounds, such as those used in polyvinyl chloride sheaths for wires, floor coverings, and plastic cabinets for electronic equipment. According to the Bureau of Mines, flame retardants now account for nearly three-fourths of domestic antimony consumption.
Transportation uses, including batteries, account for about 9 percent of U.S. consumption; various chemical uses absorb 9 percent; and miscellaneous applications account for the balance.
World mine production of antimony has dropped in the last few years, falling from 70,607 metric tons (mt) recorded in 1988 to 64,730 mt last year, according to the Bureau of Mines. Major producers include China , Bolivia , Mexico , and South Africa ; U.S. mining of antimony is fairly small, notes Llewellyn. Although domestic mining figures are not published, numbers from the half-dozen antimony smelting reveal that last year's production totaled 16,032 mt, lower than figures recorded for each of the previous four years and a big step down from 1990's 20,070 mt. One explanation for the drop, Llewellyn says, is that Chinese producers, which used to export mostly crude material, have been flooding the market with refined antimony oxides sold at a discount for the last three or four years.
China reportedly has the largest reserves of antimony. Other major holdings are in Bolivia, Mexico, South Africa, and some former Soviet republics. Stocks of primary antimony held by U.S. producers climbed from about 8,185 mt in 1990 to about 10,066 mt in 1991, according to Llewellyn. Apparent domestic consumption—based on production, imports, exports, and stocks—edged up slightly in 1991, to about 43,000 mt, from 1990's 38,963 mt.
Secondary domestic smelter production of antimony, mostly from used lead batteries but with a contribution from other alloys, has been on the rise, climbing steadily from 15,833 mt in 1987 to 20,898 mt for 1991, according to Llewellyn, who attributes the trend to increased battery recycling rates. Usually recovered as antimonial lead, secondary antimony is primarily consumed again by the battery industry, with smaller amounts ending up in other applications, such as wheel weights and ammunition.
Prices for the metal have skidded in recent years, falling from an average of about $1.11 per pound in 1987 to less than 82 cents a pound last year; prices recorded in the second quarter of this year were lower yet, bobbling around 78 to 79 cents a pound. Observers blame Chinese suppliers.
What does the future hold for antimony? Carlos Tejada, vice president of Laurel Industries (Cleveland), which produces antimony trioxide for use in flame retardants used in plastics and rubber, notes that use of antimony in flame retardants has been growing at about the same rate as the gross national product, and he predicts "modest growth" in these applications to continue for at least the next five years. With the oversupply of discounted Chinese antimony oxide likely to continue, however, near-term "prospects for Western producers of antimony are not very good," says Llewellyn.
B Is for Bismuth
Bismuth, popularly known for its contribution to Pepto Bismol®, finds its largest applications in pharmaceuticals and chemicals. Other markets include use in cosmetics and paint pigments, as well as fusible alloys. These alloys, which often combine bismuth with tin, lead, or cadmium, can be easily melted at a relatively low temperature, enabling them to help fuses function.
Bismuth is also used to improve the machinability of steels and aluminum alloys. According to Richard D. Becker, president of Metalspecialties Inc. (Fairfield, Conn.), the metal has "some funny expansion characteristics" that, combined with its strength, allow it to be used in "shuttles," which hold complicated items such as jet engine parts in place while they are machined.
The element, a silver crystalline substance with a low melting point, is a poor conductor and similar in many ways to lead, a maligned material the B-metal has been widely nominated to replace in various uses. Its relationship with lead goes even further. Generally produced as a byproduct of lead smelting (with some produced alongside copper and other metals), bismuth is mined for its own sake only in Bolivia .
The world's major bismuth producers—including Australia, Canada, China, Japan, Korea, Mexico, and Peru—supply about 4,000 mt annually. More than a quarter of this is consumed by the United States, where consumption grew about 10 percent last year, mostly because of increased chemical uses, reports Stephen M. Jasinski, mineral commodity specialist with the Bureau of Mines. (The single U.S. producer, Asarco Inc. [New York City], does not release figures on its production.) China currently provides about 25 percent of world supply and has the largest reserves—estimated at 18 percent of the world total—according to Bureau of Mines figures.
Worldwide production and consumption of bismuth in 1991 totaled 4,050 mt and 4,100 mt, respectively, according to figures compiled by the Bismuth Institute (Brussels). This year's production is expected to be similar to last year's, says one industry observer, who predicts that consumption will fall a bit. Another bismuth-watcher, however, suggests consumption is likely to rise somewhat in 1992.
Bismuth prices have been volatile over the past few decades, jumping to $20 per pound in the mid-1970s, thanks to new uses, then suffering with the recession of the early 1980s. Since reviving in the mid- and late 1980s, average annual prices in recent years have drifted down from $5.76 in 1989 to $3.10 last year. This year, notes Jasinski, they have continued to slide, dropping to about $2.50 per pound despite an apparent improvement in demand.
One industry official, noting that low prices have led to some cuts in bismuth production, says producers probably have physical inventories to meet about five month's worth of demand at current rates. The same observer cites overproduction and cuts in demand for alloys for the price softness.
Recycling has little to do with bismuth, although fusible alloys and some catalysts are recovered, generally to be consumed by the original producer. Bismuth scrap is a rarity, says Becker, who recalls the time he saw a truckload of it: "Some guy had been accumulating it for 20 years." says Becker. Most bismuth is recovered from metallurgical residues and oxides, explains Becker, whose firm refines both primary and secondary bismuth. Only "a tiny percentage" of annual bismuth consumption is secondary material, he points out, explaining that his company recycles bismuth either as service for customers or simply to keep reusable bismuth from disposal.
Nevertheless, this minor metal is seen as a "green" metal and has been nominated to substitute for other materials in a variety of applications, which might eventually mean more recycling. Use of bismuth in lead-free brass plumbing has been suggested in response to current and proposed lead-use restriction. In fact, bismuth-brass is reportedly already in production for some housing-related uses, though it's apparently facing an uphill battle. Becker, for example, calls himself "skeptical" about such applications, noting, "In brass, bismuth is usually a disaster." Some have also pointed to bismuth as a possible substitute for lead in shotgun shells and for lead and cadmium in glazes, enamels, and pigments.
Despite these potential replacement opportunities, Jasinski points out that bismuth cannot be a broad substitute for lead because its supply is limited and production is unlikely to grow more than about another 2,000 tons annually. Furthermore, he says, "it's virtually impossible to control supply—it's too coproduct-dependent." And, ironically, increased bismuth production is primarily linked to increased lead production.
Adding to these negative substitution forces, as well as difficulties bismuth-brass might make for scrap recyclers, is the fact that bismuth costs considerably more than lead. In this last regard, the substitution table is being turned on bismuth. The metal is being challenged in some of its uses by other, possibly cheaper, materials in such applications as pigments and solders. "At one time, bismuth cost close to $11 a pound and it still sold," notes one industry expert, who suggests that, today, fears of limited supply may accelerate efforts to further develop substitutes for bismuth. Nevertheless, the metal is said to be maintaining the inside track for some pharmaceutical uses and other specific applications.
One producer's representative projects a bullish future for bismuth, forecasting a consumption increase of 25 percent by 1996 and suggesting that there is a "strong possibility" consumption could double within 10 years. Becker, however, says the near-term market looks flat and points out that some promised new medical applications will be slow to develop. Taking a more middle-of-the-road view, Jasinski predicts that bismuth demand will depend on the success of its use as a substitute. But, he adds, "I think it will gradually increase," as a result of lead substitution and new pharmaceutical applications.
C is for Cadmium
Cadmium is a silver-blue metal that melts at relatively low temperatures and has a low vapor point. Similar in many ways to zinc, the metal is usually produced as a zinc byproduct, on the short end of a 1:300 ratio, according to Hugh Morrow, executive director of the Cadmium Council Inc. (Washington, D.C.). Cadmium is also produced as a byproduct of copper and lead production. Canada is the world's biggest producer. Nevertheless, Morrow notes, cadmium is fairly uniformly distributed around the world. Other major producing countries are several African nations, Australia, France, Germany, Mexico, Norway, and Russia. World primary cadmium production last year was 15,656 mt—up from 14,469 mt in 1990—according to Metal Bulletin Monthly, with U.S. production accounting for just under 1,700 mt, according to Bureau of Mines numbers. Western World cadmium consumption, meanwhile, was between 17,000 and 18,000 mt last year.
Troubled by environmental accusation and bumped from many of its uses by materials perceived as more benign, cadmium has ridden a roller coaster of demand and revulsion over the years. Applications for cadmium include consumer and industrial batteries, pigments, organic stabilizers in plastics, and corrosion-resistant coatings. It's also used in controlled-expansion devices like fire sprinklers and in infrared detectors, nuclear controls, and solar cells.
The relative importance of its various uses have shifted in recent years as it's been classed as a hazardous material but experienced success in nickel-cadmium batteries. In 1980, use in coating and plating accounted for 34 percent of U.S. domestic cadmium consumption, pigments absorbed 28 percent, batteries took 16 percent, plastic stabilizers accounted for 15 percent, and various alloys and other uses took in the balance, according to the Bureau of Mines's Llewellyn. By 1990, pigment use had dropped to 13 percent of domestic consumption, coating/plating use had fallen to 25 percent, and use in plastics stepped down a bit. Use in battery consumption, however, reportedly jumped to 40 percent (and even higher in 1991), and miscellaneous uses edged up a few points. (The Cadmium Council estimates the battery portion of 1990 cadmium consumption to be even larger, accounting for more than half.)
The metal enjoyed a surge in popularity—primarily in Japan, cadmium's largest consumer—in the late 1980s with the appearance of portable electronic equipment powered by rechargeable nickel-cadmium batteries. Cadmium's identification as a health threat—it's a suspected carcinogen and can cause kidney problems through long-term or highly-concentrated exposure—has taken a bite out of demand. Competing batteries—such as nickel hydride and lithium-based—have also dug into cadmium demand although "Ni-Cd" use continues to grow at a rate of 4 percent per year, according to Morrow.
Following the demand surge for nickel-cadmium batteries, which boosted average cadmium prices from $1.60 a pound in 1987 to more than $6 a pound through the next two years, cadmium prices slid steadily. Last year's average price was $2.01, according to Llewellyn, and this past summer, prices dropped to between 60 and 70 cents a pound. The likely culprits of this price fall? Certain "psychological characteristics" have been a problem, says Morrow, pointing to negative popular perceptions of the metal based on pending regulations by the Occupational Safety and Health Administration and proposed European Community restrictions on some of cadmium's minor uses. Department of Defense plans to sell off its stockpile of 6.3 million pounds (2,858 mt) of cadmium have added to the gloom.
Cadmium's relatively high cost and history of environmental/health questions mean that it has generally been displaced by other materials, except in "irreplaceable uses," such as in certain aerospace and military applications, where substitutions would mean inferior performance, says Morrow. On the positive side, nickel-cadmium batteries are a leading contender in the battle to be chosen as the power supply in electric vehicles—a potential boon to the cadmium industry. Nickel-cadmium batteries are lighter than lead-acid batteries, less expensive than competing nickel-hydride batteries, and well-suited to applications that require high power output, according to Morrow. Some automakers, however, reportedly fear cadmium's inelastic supply and the metal's clearly demonstrated price volatility.
Large-scale recycling of cadmium, especially in batteries, is a fairly recent development, with only a handful of recyclers active in Japan, Europe, and the United States. One of the few, INMETCO (Ellwood City, Pa.) recovers cadmium from specialty steel mill residues and nickel-cadmium batteries. Another firm, Horsehead Resource Development Co. Inc. (Monaca, Pa.), assists INMETCO and also retrieves cadmium directly from electric-arc furnace dust.
Recycling of nickel-cadmium batteries, however—especially small consumer units, which are often difficult to remove from appliances—has barely begun. (Several states are leaning on manufacturers to make consumer nickel-cadmium batteries easier to remove and recycle.) Nevertheless, the Cadmium Council hopes to boost recycling of nickel-cadmium consumer batteries to a 30-percent rate and meet or beat the comparable recycling rate for lead-acid industrial batteries, Morrow says.
How important is recycling to cadmium's future? "It's the only way the market will succeed or endure," predicts Morrow. Llewellyn suggests, however, that profitable recycling of cadmium requires a market price of $2 to $3 a pound, far better than current values. •
Antimony, bismuth, and cadmium fill narrow but vital niches in a variety of industries.