Korea Zinc's Onsan smelter in the Onsan National Industrial Complex, a 40-minute drive from Ulsan Station, spans approximately 1.41 million square meters—18 times the size of Seoul World Cup Stadium. This facility, the heart of Korea Zinc and the target of a strategic partnership overture from the U.S. Department of Defense, produces more than 1 million tons annually of over 10 types of metals, ranging from base metals such as zinc, lead, and copper to precious metals including gold and silver, as well as defense-critical materials like antimony.
The first stop was the country's only indium processing line. Forty vacuum-packed indium bars weighing 5 kilograms each, with 99.999% purity, produced the previous day were stacked in storage. Each bar is worth approximately 5 million won and serves as an essential material for semiconductor substrates and solar panels. About 90% of production is exported to the United States, Japan, and Taiwan.
"Global indium production is inherently limited," said Jongbin Jeon, head of Korea Zinc's electronic materials team. "Korea Zinc's strength lies in extracting indium from waste solar panels without any loss." This represents a modern-day alchemy that transforms waste into advanced industrial materials.
Korea Zinc does not discard byproducts from its zinc, lead, and copper smelting processes. Instead, the company circulates and concentrates them to mass-produce rare metals including antimony, indium, and bismuth. By reprocessing byproducts from various smelting processes to increase concentration rates, Korea Zinc has achieved world-leading quality in rare metal production and recycling ratios.
By minimizing waste while maximizing extraction of strategic minerals, the company's financial performance has soared. Korea Zinc reported consolidated revenue of 16.58 trillion won and operating profit of 1.23 trillion won last year, up 37.6% and 70.3% year-over-year, respectively.
Zinc, the flagship product of Onsan smelter, is produced at 630,000 tons annually and shipped to domestic and international steelmakers including POSCO and Hyundai Steel. This represents the largest output among single smelters worldwide. If steel is the rice of industry, zinc—which prevents corrosion in steel products—could be called industry's vitamin.
Korea Zinc's proprietary "low-temperature, low-pressure hematite process," the only commercially viable technology of its kind globally, removes iron impurities at lower temperatures and pressures than conventional methods, achieving zinc recovery rates of up to 99%. This is why the Ministry of Trade, Industry and Energy designated the process as a national core technology last year.
The dedicated wharf receiving raw materials from South America, including Bolivia, was filled with piles of ore and rock being unloaded. Learning that these materials would be transformed into rare metals such as antimony for weapons manufacturing at Onsan smelter underscored just how significant a single company's strategic security value can be.
Korea Zinc has been exporting antimony to the United States since last year for use in armor-piercing ammunition alloys, military electronics, and aerospace alloys, with orders continuing to grow. Onsan smelter produces approximately 10 tons of antimony daily and 300 tons monthly—a metal previously supplied almost exclusively by China—establishing itself as a production base the U.S. Department of Defense considers a trusted partner. Additionally, gallium and germanium, strategic minerals used in semiconductors, telecommunications, and military equipment, will be produced at Onsan smelter starting next year to replace Chinese supply chains.
In response to U.S. interest, Korea Zinc is accelerating its project to build a smelter in Clarksville, Tennessee, with capacity roughly half that of the 1.1-million-ton Onsan facility. "We have assembled about 70 specialists to handle equipment procurement and manufacturing for the U.S. plant," said Seunghyun Kim, head of Onsan smelter. The Clarksville facility will replicate Onsan's zinc, lead, and integrated processing operations.
Korea Zinc is simultaneously transforming Onsan smelter into a smart factory. "We have deployed Boston Dynamics' quadruped robot 'Spot' for round-the-clock facility inspections," Kim said. "We plan to expand the robot fleet based on performance results."
