Zinc "Coat" – A Historical Perspective on the Use of Zinc in China
China was the first country to discover and utilize zinc. In 1922, Wang Tong conducted a chemical analysis of ancient Chinese coins and found traces of zinc. This discovery sparked further research. In 1923, Zhang Hongjun published two significant works, “The Origin of Zinc in China†and “Re-Discussing the Origin of Zinc in China.†Based on historical texts and the analysis of ancient currency, he concluded that zinc was used as early as the Han Dynasty (1st century BCE).
The use of zinc in China began with the production of brass, an alloy of copper and zinc. During the Han Dynasty, there was a law prohibiting the use of “pseudo-gold,†which scholars now believe refers to brass. In texts from the Northern and Southern Dynasties (4th century AD), the term “meteorite†appeared, which later research suggests referred to brass. By the Tang Dynasty, it was recorded that brass was produced from “calcium,†meaning zinc carbonate. One passage from the “Tang Shu: Food and Drink†states: “During the reign of Xuanzong (712–755), there were ninety-nine furnaces, each casting 3,300 bolts of silk and producing 21,200 jin of brass.â€
The Ming-era text “Tiangong Kaiwu†provides more detailed information on brass refining. It describes the process: “For every six pounds of red copper, four pounds of lead are added to the pot, melted, and then cooled to form brass.†Here, “red copper†refers to copper, and “lead lead†refers to zinc.
The earliest known smelting of metallic zinc in China dates back to the Ming Dynasty. The “Hardware†chapter in “Tiangong Kaiwu†describes how to refine “lead lead†(zinc) from “burning stone†(zinc carbonate). Zinc is easier to smelt than iron or copper because its melting point is only 419°C and boiling point is 907°C. When heated above 1000°C, zinc can be reduced from its ore using coke, forming vapor that condenses into pure zinc crystals. For many years, it was believed that the British were the first to develop this technique, patenting it in 1739. However, research shows that the method was likely adopted from China around 1730.
According to Jinan black and white iron processing, by the 16th and 17th centuries, China was producing zinc with up to 98% purity, which was transported to Europe by Western trading companies like the East India Company. Eventually, the smelting techniques also spread to Europe. Today, some European countries still refer to zinc as “Dutch Tin,†due to the involvement of Dutch, British, French, and Portuguese traders. This name is misleading, as the true origin of this metal is Chinese.
Zinc is a silvery-white metal commonly used for coating tin to prevent rust. When exposed to air, zinc develops a blue-gray oxide layer, which is dense and protective. This property makes zinc ideal for galvanizing iron and steel. About 40% of global zinc production is used in making tinplate, which is used in pipes, barrels, and other containers.
Jinan black and white iron processing notes that zinc-coated materials are more durable than regular tinplate. While tinplate may corrode quickly if damaged, zinc-plated surfaces remain resistant to rust due to zinc’s higher reactivity. Zinc is also used in dry batteries and in the production of brass, an alloy of copper and zinc.
One of the most important zinc compounds is zinc oxide, also known as “zinc white,†a common white pigment used in paints. It turns yellow when heated and returns to white when cooled, making it useful in color-changing thermometers. Zinc is essential for plant growth, with zinc sulfate being a key micronutrient fertilizer. Some plants contain high levels of zinc, such as psyllium and celery, while certain cereals may have up to 12% zinc content.
In the human body, zinc is present in small amounts, mainly in teeth and the nervous system. Fish transfer most of their zinc to eggs before spawning. Zinc is found in the Earth's crust at about 1 part per 100,000. The most common ore is sphalerite, a zinc sulfide mineral used in industrial zinc smelting. In 1971, global zinc production reached 3.7 million tons.
Jinan black and white iron processing also highlights that zinc is often confused with lead. Galvanized iron wire is sometimes called “lead wire,†and galvanized sheets may be mistakenly referred to as “lead skin.†These terms should be corrected. Industry insiders note that while the base material of tinplate may not be as strong as Q235 steel, it is less expensive and more resistant to rust. Galvanized iron sheets, commonly known as “white iron,†are widely used for roofing, piping, and containers. Ungalvanized iron is referred to as “black iron.â€
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